Potentials of Crop Residues for Commercial Energy Production in China a Geographic and Economic...

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Potentials of crop residues for commercial energy

production in China: A geographic and economic

analysis

Huanguang Qiu a, Laixiang Sun b,c,d,*, Xinliang Xu e, Yaqing Cai e, Junfei Bai f

a School of Agricultural Economics & Rural Development, Renmin University of China, 59 Zhongguancun Ave, Beijing

100872, Chinab Department of Geographical Sciences, University of Maryland, College Park, MD 20742, USAc Department of Financial & Management Studies, SOAS, University of London, London WC1H 0GX, UKd International Institute for Applied Systems Analysis (IIASA), A-2361 Laxenburg, Austriae Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Jia 11, Datun Road,

Anwai, Beijing 100101, Chinaf College of Economics and Management, China Agricultural University, 17 Qinghua East Road, Haidian District,

Beijing 100083, China

a r t i c l e i n f o

Article history:

Received 14 July 2012

Received in revised form

17 February 2014

Accepted 25 March 2014

Available online 21 April 2014

Keywords:

Crop residue

Bioenergy

GIS

Relative prices

China

a b s t r a c t

China has become increasingly dependent on the international energy market owing to the

rapid growth of demand for energy. To develop renewable energy and thus strengthen

energy security for the future, it is important to consider the potential of crop residues.

This paper contributes to this topic by mobilizing up-to-date statistical and remote-sensing

data and by carrying out a geographic and economic analysis. Its assessment shows that

China’s total output of crop residues in 2010 amounted to 729 million tons, and the

quantity could be used for commercial energy production is between 147 and 334 million

tons, depending on the competition power of the commercial energy production relative to

the traditional uses of crop residues. The analysis also shows that the distribution of crop

residues in China is highly uneven. By taking into account the densities of crop residues

available for energy production at the grid-cell level, the transportation cost constraints,

and the economy-of-scale requirements of energy plants, this study further assesses the

geographic distribution of the suitability for establishing crop residue based power plants

and bioenergy plants in China.

ª 2014 Elsevier Ltd. All rights reserved.

1. Introduction

The growing scarcity of fossil energy and the high level of

energy prices have stimulated the wide-reaching efforts to

develop bioenergy. Starting from the early 1990s and espe-

cially since 2000, the biofuel and biodiesel industry has begun

to play an important role in energy supply to moderately

alleviate global energy shortages [1]. However, the feedstock

of current biofuel production consists of mainly seeds of grain

* Corresponding author. Department of Geographical Sciences, University of Maryland, LeFrak Hall, College Park, MD 20742, USA.E-mail addresses: [email protected], [email protected] (L. Sun).

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crops, oil-bearing crops, and sugar crops. This leads to a food-

fuel competition for agricultural products, adding pressure on

worldwide food security [2]. To reduce this tension, many

countries have started to pay attention to crop residues and

other biomass for energy production.

The impressive economic growth of China has led to rapid

rises in both energy use and food consumption. How to

improve China’s energy security without undermining itsfood security has become one of the top policy issues within

the country and beyond. In 2013, China’s import of crude oil

reached 280 million tons, which accounted for 58 percent of

the nation’s total oil consumption in the year [3]. A widely

reported projection of the International Energy Agency sug-

gests that about 75 percent of China’s oil consumption will

have to be imported by 2030 [4]. The growing consumption of

energy has also given rise to mounting concerns on green-

house gas emissions [5]. It is also worth noting that despite its

success in agricultural development, China has become a net

importer of agricultural commodities since 2004, with the

total trade deficit in the sector reaching 49.19 billion USD in

2012 [6]. A leading example is that China’s import of soybeanin 2012 reached 58.4 million tons, accounting for about 80% of

China’s total soybean demand [7]. It is expected that China’s

imports of soybean and maize will continue to increase in the

future, largely driven by the rising demand for meat and

vegetable oil [8].

To address the joint issue of energy security and food

security, China’s strategy on renewable energy development

has been to put a great emphasis on the utilization of crop

residues for commercial bioenergy production. According to

the Medium- and Long-Term Development Plan for China’s

Renewable Energy issued in 2007, the share of renewable

energy in total energy consumption is expected to increase

from 10 percent in 2010 to 15 percent in 2020. The target forthe capacity of power plants using renewable biomass such

as crop residues is set at 3107 kW and the target for the

annual production of biomass pellet fuel is set at 50 million

tons [9].

Although the targets are clearly set, there has been an

ongoing debate in regard to the quantity of crop residues that

can be mobilized for commercial bioenergy production.

Existing studies show wide differences between their esti-

mations on the potential quantities of crop residues that can

be effectively utilized for bioenergy production in China.

Furthermore, most of the studies focus on estimating the total

amount (also called theoretical amount) and the collectable

amount of crop residues, without consideration of thecompetitive uses of these residues for other purposes, such as

animal feed, organic fertilizers, and raw materials for paper

making and other industries. These competitive uses will

become increasingly sensitive to the rise in the farm-gate

prices of crop residues if the demand from bioenergy pro-

duction becomes sufficiently high.

For example, the theoretical amount of crop residue pro-

duction in 2006 was put at 433million tons in Cui et al. [10] and

728 million tons in Shen et al. [11,12], showing a large gap of

295 million tons. The collectable amount of crop residues in

2006 was put at 372 million tons by a study of the Chinese

Academy of Agricultural Engineering [10] and at 686 million

tons by Wang et al. [13]. There are even greater divergences

among existing research on the amounts of crop residues

which could be used for biomass energy production. With the

implicit assumption that bioenergy production will not

compete with the traditional uses such as livestock feed,

organic fertilizer, rural conventional fuel energy, and indus-

trial raw materials, Cui et al. [10] suggest a quantity of 176

million tons for 2006 and Yang et al. [14] suggest a quantity of

331 million tons for 2007. By considering a part of the tradi-tional uses of crop residues as a binding conservation

requirement and thus free from economic competition, Jiang

et al. [15] suggest a figure of 807 million tons as the theoretical

quantity and 506 million tons as available for biomass energy

production.

One key reason which leads to the big discrepancy in

theoretical quantity estimation is the obvious differences in

the ratios of residues to main products employed in different

research. Such differences, in combination with different as-

sumptions on the rates for the traditional utilization of crop

residues, result in even greater divergences in the estimation

of the amount available for commercial bioenergy production.

Another issue worth considering is that few studies look at thecosts of collecting, storing and utilizing the available crop

residues for energy production. In comparison with grain, the

volume of crop residues per unit of cropland is typicallylarger,

the weight per unit of volume is lighter, and the costs of

collection, transportation and storage are often much higher.

These constraining factors vary significantly across

geographical space and therefore it is important to analyze

the spatial distribution and the density of crop residue

resource in different regions.

This paper reassesses the potentials of crop residues for

commercial energy production in China by mobilizing up-to-

date statistical and remote-sensing data and conducting a

geographic and economic analysis. For the crop-specific ratioof residues to main products, we take the median values of

the diverse ratios employed in existing publications. By

taking into account the densities of crop residues available

for energy production at the grid-cell level, the trans-

portation cost constraints, and the economy-of-scale re-

quirements of energy production plants, this study further

investigates the geographic distribution of the suitability for

establishing crop residue based power plants and bioenergy

plants in China.

2. Methodology

2.1. Theoretical and collectable amounts of crop residues

Crop residues (CRs) are the biomass of crops excluding the

main products. CRs typically include stalks, leaves, and roots.

The theoretical amount of CRs is given by:

CR ¼Xn

i¼1

Qci$ri; (1)

where CR is the theoretical amount of crop residue, Qci is the

output of main products of crop i. Using maize as an example,

Qci represents the total output of corns. ri is the quantity ratio

of crop residues to main products of crop i.

b i o m a s s a n d b i o e n e r g y 6 4 ( 2 0 1 4 ) 1 1 0 e1 2 3 111







Collectable amount of CRs refers to the maximal quantity

of CRs that can be collectedfrom fields under theconditions of

current cultivation management practices. It excludes the

parts that are usually not collected, such as crop roots and the

lower part of the stalk not harvested [13]. Collectable amount

of CRs is obtained by multiplying the theoretical amount with

the collection coefficient as presented in Eq. (2).

CRA ¼Xn

i¼1

Qci$ri$ f i; (2)

in which CR A is the collectable amount and f i is the collection

coefficient of crop i. Several factors can affect the collection

coefficient, including the characteristics of the crops and the

harvesting practice. The collection coefficient is usually lower

under mechanical harvesting system than under manual

harvesting system [10,13].

2.2. Potential quantity of crop residues for commercial

energy production

Collectable CRs have multiple uses, in addition to serving as

input into commercial energy production. For thousands of

years, Chinese peasants have used CRs as animal feed, as fuel

for cooking and heating, and to generate organic fertilizers.

The current allocation of CRs across different uses is largely

determined by the levels of economic development and

industrialization in various regions. In this study, we assume

that the use of CRs as industrial raw materials (mainly in the

paper industry) would keep its competitiveness vis-a-vis the

newly arrived use for commercial energy production, the

utilization of CRs for organic fertilizers would not be

compromised by the arrival of the new demand owing to the

public awareness of the importance of agro-ecological con-servation and furthermore the concerns regarding food se-

curity. It is also assumed that the use of crop residues as

livestock feed will not be compromised owing to the foreseen

significant increase in demand for livestock products [8].

In contrast, we assume that the use of CRs as conventional

fuels for rural household heating and cooking will be sensitive

to the rise of farm-gate prices of CRs in line with the

rising demand driven by commercial bioenergy production,

because the substitutive fuels will become relatively cheaper

compared with crop residues. We consider three scenarios

with regard to this sensitivity: (A) those crop residues that are

currently wasted can be utilized for commercial bioenergy

production and other traditional uses keep their currentshares; (B) 50 percent of the household conventional use for

heating and cooking will be further shifted to bioenergy pro-

duction, and(C) 100 percent of household conventional use for

heating and cooking will be shifted to bioenergy production.

Based on above assumptions, the amount of CRs that could be

used for commercial bioenergy production can be calculated

as following:

CRE ¼Xn

i¼1

Qci$ri$ f i$ei: (3)

In Eq. (3), CRE is the amount of CRs that can be used for

bioenergy production and ei is the share of CRs that could be

used for bioenergy production in the total collectable CRs,

which has three scenario values in line with our assumptions

discussed above.

2.3. Spatial distribution of the crop residue resource for

commercial energy production

Economically attainable quantity of CRs for commercial bio-energy production critically depends on the spatial distribu-

tion of CRs in terms of output density. The technical flow-

chart for calculating such yield distribution is presented in

Fig. 1. The net primary productivity (NPP) map we employ for

this calculation is at the 11 km grid level.

As indicated in Fig. 1, using methods presented in Sections

2.1 and 2.2, we first calculate the theoretical amount (CR), the

collectable amount (CR A), and the amount that could be used

for commercial energy production (CRE) at the county level.

The output of main products Qc i is obtained from the official

statistics at the county level. The parameter ri takes the me-

dian value of existing 16 research works for given i (at the

national level), f i takes the mean value of 4 possible parame-ters suggested in two publications for given i (at the national

level), and ei is collected and calibrated at provincial level

following the assumptions in Section 2.2 and then applied to

each county in the same province. The formula for calculating

the density of crop residue resources for commercial energy

production is as follows:

Dcg ¼ ðCREÞcP

g˛cNPPg NPPg; (4)

in which Dcg is the density of CR resources potentially avail-

able for commercial energy production in given grid cell g,

(CRE)c is the total amount of CRE given by Eq. (3) in county c,

NPPg isthe value ofNPPin gridcell g, which is estimated basedon the GLO-PEM Model [16]. The GLO-PEM model is a pro-

duction efficiency model, which consists of linked

Output of main products of

crops (county level data)

Ratio of residues to main

products

Theoretical amount of cropresidues Collectionratio

Collectable amount of

crop residuesScenarios on economic

trade-offs

Potentials of residues for energy

production in each county

NPP map

Total NPP in

each county

Amounts of residue for energy production

per unit of NPP in each county

Density map of crop residue

resources in energy production

Fig. 1 e Technological flow chart for estimating the density

distribution of crop residue resources for bioenergy

production.








c- omponents that describe the processes of canopy radiation

absorption, utilization, autotrophic respiration, and the

regulation of these processes by environmental factors such

as temperature, water vapor pressure deficit, and soil mois-

ture [17e19]. The map of cropland, with a resolution of

11 km, is generated from the 2005 nationwide land cover/use

datasets of the Chinese Academy of Sciences [20]. The map

presents cropland area as a percentage of the 11 km grid.Within each 11 km grid, the NPP was calculated on cropland

area. Eq. (4) uses the grid level NPP values to distribute the

county level CRE to individual grid cells of farmland in the

given county.

Once the quantity of CRE becomes available at the grid-cell

level, we further analyze the spatial distribution of suitability

for constructing CR-based biofuel plants or power plants in

different areas. Drawing advice from existing studies, we

choose the economically viable radius for a biofuel or power

plant to collect CRE within the circle defined by the radius. The

economically viable quantity of CRE in the circle is obtained by

summing CRE across grid cells within the circle. Matching the

economically viable quantity of CRE in the circle with the totalfeedstock demand of operationally viable plants, we assess

the suitability for constructing crop residue based power

plants or bioenergy plants in different regions.

3. Key parameters

3.1. Ratio of residues to main products and collection

coefficient

Table 1 reports the crop-specific ratios of crop residues to

main product in terms of physical weight of dry matter

employed in various studies. It shows a great variation acrossthe listed studies. Several reasons may cause such variation: a

given crop may grow in different periods of a multi-cropping

system and this leads to differences in the ratio; continu-

ously growing the same crop without paying sufficient

attention to the rotational requirement of cropping agricul-

ture may lead to changes in the ratio; for the same crop,

different varieties may also bear different ratio of residues to

main product. Owing to these reasons, each ratio given in the

existing research may have its own emphasis and it is difficult

to find which one has more merits than others. Therefore in

this research, we take the median value of these ratios as

presented in Table 1.

Table 2 shows the crop-specific collection coefficients of crop residue employed by two influential studies. In recent

years, the mechanized harvesting has become increasingly

popular, which led to the decline of collection coefficient of

crop residues. According to latest official statistics, the share

of sown areas harvested by harvesters in China was about

27.5% of the total sown area, and the shares for rice, wheat,

maize and rapeseed are 46.3%, 92.4%, 9.7% and 6.0%, respec-

tively [30]. With reference to the shares of mechanically and

manually harvested areas of different crops and the corre-

sponding collection coefficients employed in Ref. [10], this

research calibrates national level collection coefficients for

rice, wheat, maize and rapeseed by taking additional assis-

tance from expert opinions, as reported in Table 2. For the T a b l e

1

e

R e s i d u e

t o

P r o d u c t R a t i o

( R P

R ) o f v a r i o u s c r o p s .

Y u k i h i k o

T s u m u r a e t a l . ,

2 0 0 5 [ 2 1 ]

H . L i u e t a

l . ,

2 0 0 8 [ 2 2 ]

K i m &

D a l e ,

2 0 0 4 [ 2 3 ]

X . Z e n g e t a l . ,

2 0 0 7 [ 2 4 ]

L a l ,

2 0 0 5 [ 2 5 ]

S h e n e t a l . ,

2 0 1 0 [ 1 1 ]

C u i e t a l . ,

2 0 0 8 [ 1 0 ]

S o n g ,

2 0 1 0 [ 1 ]

J i a

,

2 0 0 6

[ 2 6 ]

B i ,

2 0 1 0 [ 2 7 ]

M i n i s t r y o f

S c i e n c e & T e c h ,

1 9 9 9 [ 2 8 ]

R e n

e w a b l e

e n e r g

y p r o j e c t ,

2 0

0 8 [ 2 9 ]

M e d i a n

R i c e

2 . 5 3

1 . 3 3 6

1 . 3

1 . 3 4

1 . 5

1 . 1

0 . 7 3

1 . 1

0 . 7

3

1 . 3

1 . 2 8

1 . 3 7

1 . 3

W h e a t

1 . 4 3

0 . 6 2 3

1 . 4

0 . 6 2

1 . 5

1

0 . 6 8

1 . 1

0 . 7

8

0 . 9 5

0 . 9 5

0 . 6 2

0 . 9 5

M a i z e

1 . 1

2

1

2

1

2

1 . 2 5

2

0 . 9

1 . 1

1 . 2 5

2

1 . 2 5

T u b e r c r o p s

1 . 1 4

0 . 5

e

0 . 5

0 . 2 5

1

1

1 . 2

e

0 . 9 6

0 . 5

0 . 5

0 . 7

3

S o r g h u m

1 . 5 7

e

1 . 3

e

1 . 5

2

e

2

e

1 . 6

e

1 . 5

8 5

S o y b e a n

2 . 1 4

1 . 5

e

1 . 5

1

1 . 7

e

2

0 . 7

5

1 . 6

1 . 5

1 . 5

1 . 5

P e a n u t

e

e

e

2

e

1 . 5

e

2

e

1 . 5

2 . 2 1

2

2

R a p e s e e d

e

2

e

2

1 . 5

3

1 . 0 1

3

1 . 2

9

2 . 7

2 . 2 1

2

2

S e s a m e

e

2

e

2

e

2

1 . 0 1

3

e

2 . 8

2 . 2 1

2

2

S u n fl o w e r

e

2

e

2

e

2

1 . 0 1

3

e

2 . 8

2 . 2 1

2

2

O i l fl a x

e

2

e

2

e

2

1 . 0 1

2

e

2

2 . 2 1

2

2

F i b e r c r o p s

e

2 . 5

e

2 . 5

e

e

e

1 . 7

e

1 . 9

e

e

2 . 2

C o t t o n

e

3

e

3

1 . 5

3

5 . 5 1

3

3 . 5

3

5

3 . 1 4

3

3

S u g a r c a n e

0 . 5 2

0 . 1

0 . 6

0 . 1

0 . 2 5

e

e

0 . 1

e

0 . 2 4

0 . 1

0 . 2 5

0 . 2 4

S o u r c e : L i t e r a t u r e r e v i e w c o n d u c t e d b y t h e a u t h o r s .








collection coefficients of other crops including peanut, ses-

ame, sunflower, and oil flax, owing to the lack of statistics on

mechanically and manually harvested areas, we have to take

the average of the coefficients employed in Cui et al. [10] and

Wang et al. [13].

3.2. Rates for competitive and alternative uses of crop

residues

As discussed before, owing to historical and ecological rea-

sons as well as the transportation constraints in remote areas,

the collectable crop residues have been mainly utilized as

livestock feed, organic fertilizers, industrial raw materials of paper making industry, and traditional heating and cooking

fuels in rural areas. In this section, we carefully assess to what

extent these existing uses may give way to commercial energy

production.

In terms of crop residues as livestock feed, the existing

literature indicates that since 2000 the proportion has been

about 22.6e27.5% in the total amount of collectable crop res-

idues [29,31,32]. In this research, we conduct the estimation at

the provincial level and employ the following calculation

procedure: (a) In cropping areas, we assume that the annual

quantity of residues and fodder consumed by large animals,

such as cattle,horse, donkey, mule and camel, is 1274 kg/head

[29], and for medium-sized livestock like sheep and goats thecorresponding figure is 570 kg/head [33]. We ignore con-

sumption of crop residues by small animals like poultry given

the limited use of crop residues in poultry feed. The total de-

mand for crop residues and fodder grass in each province is

calculated by multiplying the average animal inventory be-

tween the beginning and the end of theyearwiththe per-head

demand, and the demand for crop residues is the above total

demand minus the total fodder production from grasslands.

(b) In semi-pasture area, the calculation approach is similar as

above but with the assumption that one half of the total folder

supply is from the pasture land and the otherhalfis from crop

residues. The results of our estimation are showed in the 3rd

column of Table 3. Witnessing the significant increase in

demand for livestock products in recent decades and fore-

seeing a further increase of such demand in coming decades

[8], we assume that the use of crop residues as livestock feed

would not be compromised by the competitive demand from

the commercial energy production.

Using crop residues as organic fertilizer is an important

means to maintain and further improve soil organic content

and fertility. Cui et al. [10] and Wang et al. [13] estimate that

under current cropping practices, the appropriate proportion

of collectable crop residues that should be used for main-

taining farmland fertility is between 15 and 18.5%. Based on

our own more regional specificinvestigation, we estimate that

the proportion of collected crop residues being returned tofarmland as fertilizer is about 20% in Loess Plateau, Mongolia-

Xinjiang region, Qinghai-Tibet Plateau and North China, 15%

in Northeast China and Southwest China and 12% in the other

regions (4th column of Table 3). Given the increasing concern

on food security and the growing public awareness of the

importance of agro-ecological conservation, we assume that

the utilization of crop residues for organic fertilizers would

not be compromised by the competition from the commercial

energy production.

The paper production industry has been the dominant use

of crop residues in the category of industrial raw material.

Paper industry might continue to be economicallycompetitive

in terms of competing with bioenergy production for cropresidue resources. On the other hand, the increasing public

awareness of environmental pollution caused by the paper

industry in general and small scale paper-producing plants in

particular has led to the closing of a large number of small

paper-making plants in recent years. This has resulted in a

reduced share of non-wood paper production in the industry

during the last decade [34]. In 2010, 12.97 million tons of non-

wood paper was produced, with the input of 20 million tons of

wheat stalk [35], which accounted for about 30% of the total

output of wheat stalk in the year. In consideration of the

existing progress made and the new efforts committed by the

industry in pursuing economy of scale and controlling pollu-

tion, this study assumes that the proportion of wheat stalk as

Table 2 e Collection coefficients of crop residues by crop.

Ming Cui [10] Yajing Wang [13] Value of this study

Coefficient of mechanized harvesting

Coefficient of manual harvesting

Collectioncoefficient

Collection coefficient Collection coefficient

Rice 0.66 0.90 0.78 0.75

Wheat 0.77 0.90 0.76 0.83 0.75

Maize 1.00 1.00 0.95 0.95Tuber crops e e e 0.80 0.80

Other cereal crops e e e 0.80 0.80

Sorghum e e e 0.80 0.80

Legume crops e e e 0.88 0.88

Peanut 0.85 0.95 0.90 0.85 0.88

Rapeseed 0.85 0.95 0.90 0.85 0.89

Sesame 0.85 0.95 0.90 0.85 0.88

Sunflower 0.85 0.95 0.90 0.85 0.88

Oil flax 0.85 0.95 0.90 0.85 0.88

Cotton e 0.94 0.89 0.90 0.90

Fiber crops e e e 0.87 0.87

Sugar crops e e e 0.88 0.88

Source: Literature review and interviews with experts in the field conducted by the authors








an input to the paper production industry will remain at the

level of 30% in the total collectable in most provinces. In thoseprovinces where the total collectable amount of wheat resi-

dues is less than 1.5 million tons, we assume that no wheat

residues will be used for paper production owing to the lack of

economy of scale. Crop residues are also popular inputs to

mushroom production. We assume that the ratio of crop

residue use to the output of mushroom production is 1:1. The

output of mushroom production in individual provinces is

taken from Yearbook of China Agricultural Products Processing

Industries [36].

Direct burning crop residues for cooking and heating has

been the conventional way of using crop residues as bio-fuel

in rural China, which has a very low level of energy effi-

ciency as heat is allowed to escape into the open air. Theemphasis of this paper is on modern commercial ways of

utilization such as power generation and bioethanol produc-

tion, which significantly improve the energy efficiency. The

recent economic development experienced in China has

resulted in a declining share of crop residues in total rural fuel

energy consumption [37]. A number of studies show that the

conventional use of crop residue as cooking and heating fuels

takes up about 23.7e50.0% of the total amount of collectable

crop residues [29,31,32,38]. Based on multiple sources and

fieldworks, Bi [27] conducts a detailed and careful investiga-

tion of crop residue consumption per household for different

regions of China. We mainly adopt Bi’s results with necessary

modifications according to relative distribution patterns

across provinces as given in China Energy Statistics Yearbook

and other relevant information in Refs. [10,13,31]. The share of crop residue directly burned for rural household cooking and

heating is shown in the 2nd column of Table 3.

It is also worth noting that a significant proportion of crop

residues have been simply wasted in rural China. The last

column of Table 3 shows the shares of such wasted crop

residue in the total across different provinces. For example, in

Heilongjing province, the share of wasted crop residue is

estimated to be as high as 40.3%. Due to various reasons such

as the lack of market demand or abundance in exceeding the

level of rural households’ own use, some crop residues are

wastefully burnt on land afterharvesting or being taken out of

the land and then abandoned. In this study, we consider three

scenarios in calculating the potential quantity of crop residuesthat could be used for commercial bioenergy production. In all

three scenarios, we assume that with appropriate policy

support, those crop residues being currently wasted or aban-

doned can be used for commercial bioenergy production. For

scenarios B and C, as discussed in Section 2.2, once farm-gate

prices for crop residues become sufficiently high owing to the

rising demand from the modern bioenergy sector, the use of

crop residues for conventional rural fuel energy will decline.

More specifically, in Scenario B, we assume that 50% of the

current household use for conventional fuel energy will give

way to bioenergy production, which is very likely in the me-

dium term; and in Scenario C, we assume that 100 percent of

current household use for conventional fuel will give way to

Table 3 e Current shares of alternative use of crop residues by province (%).

Rural fuel energy Livestock feed Organic fertilizer Industrial raw materials Wasted or not used

Beijing 26.8 36 20 3 14.2

Tianjing 35.1 26.8 20 3.1 15

Hebei 27.3 29.1 20 10 13.6

Shandong 24.5 35 12 11.4 17.1

Henan 22.7 21 12 14.8 29.5

Liaoning 36.3 34.4 15 2.5 11.8

Jilin 22.1 21.5 15 1.2 40.3

Heilongjiang 25.5 18.1 15 1.4 40

Shanxi 39.3 36.2 20 0.5 3.9

Shaanxi 33.8 27.4 20 11.4 7.4

Gansu 35.6 27.4 20 6.1 10.9

Inner Mongolia 26.3 33.8 20 1.9 18

Ningxia 20.4 45.9 20 0.2 13.5

Xinjiang 21.2 28.1 20 4.2 26.5

Tibet 39 36.9 20 0 4.1

Qinghai 39 35.7 20 0 5.3

Shanghai 25 17.8 12 7.3 37.9

Jiangsu 30.5 8.3 12 14.3 34.9

Zhejiang 32.6 14.8 12 1.3 39.3

Anhui 28.6 15 12 10.2 34.2

Hubei 30.1 24 12 3.1 30.8

Hunan 38.8 31.5 12 2.7 14.9

Jiangxi 36.7 17.4 12 2 31.9

Chongqing 46.4 19 15 0.7 18.9

Sichuan 51.9 23.4 15 6 3.8

Guizhou 46.4 24.2 15 0.3 14.1

Yunnan 47.8 24.2 15 0.3 12.7

Fujian 30.8 22.7 12 20 14.6

Guangdong 32.3 23.7 12 2.1 29.9

Guangxi 29.8 22.5 12 0.8 34.9

Hainan 25 14.6 12 1.5 46.9








bioenergy production, which is likely in the long term and

might be a very optimistic scenario in favor of commercial

bioenergy production.

To summarize, Table 3 presents the shares of alternative

uses of crop residues in the total collectable at the provincial

level.

4. Results

4.1. Potential of crop residues for commercial energy

production

We apply the methods and parameters presented in Sections

2.1 and 3.1 to the 2010 official statistical data on the total

output of the main products of each crop as listed in Table 1.

This application generates the theoretical amount and the

collectable amount of crop residues at the county level. We

then calculated the potentials of crop residues that could be

used for commercial energy production under the three

different scenarios as we specified in Section 2.2. Table 4

presents the results of these calculations.

From Table 4 we can see that in 2010 the total theoretical

output of crop residues in China was 729 million tons and the

top-three contributors were 222, 186, and 150 million tons

from maize, rice and wheat, respectively. The top-three crops

accounted for 76.5% of the total theoretical amount. Theregional distribution of the theoretical amounts were 188, 116,

42, 58, 3, 175, 86, and 59 million tons in the North China Plain,

Northeast China, Loess Plateau, Northwest, Qinghai-Tibet

Plateau, Central and East China (Lower and Middle Reaches

of Yangtze River), Southwest China and South China,

respectively. At provincial level, Henan Province in the North

China Plain ranked first with 80 million tons in 2010, whereas

Tibet was the least with only 1 million tons. The total amount

of China’s collectable crop residues in 2010 was 609 million

tons and its regional distribution was very similar to that of

the theoretical amount.

Table 4 e Potential of crop residues for bioenergy production, by region and province (million tons).

Theoretical amount Collectable amount Potentials for bioenergy production

Scenario A Scenario B Scenario C

China 728.63 609.44 147.10 240.69 334.32

North 188.30 157.56 33.73 53.06 72.39

Beijing 1.49 1.33 0.19 0.37 0.54

Tianjin 2.19 1.90 0.29 0.62 0.95

Hebei 41.73 35.67 4.85 9.72 14.59

Shandong 63.02 53.20 9.10 15.61 22.13

Henan 79.87 65.46 19.31 26.74 34.17

Northeast 116.30 103.14 35.70 49.36 63.05

Liaoning 22.36 20.03 2.36 6.00 9.64

Jilin 34.96 31.70 12.78 16.25 19.75Heilongjiang 58.98 51.40 20.56 27.11 33.67

Loess Plateau 42.18 36.59 2.64 9.28 15.91

Shanxi 14.13 12.64 0.49 2.99 5.47

Shaanxi 15.50 13.21 0.98 3.21 5.44

Gansu 12.55 10.75 1.17 3.09 5.00

Northwest 58.17 51.07 10.80 16.87 22.94

Inner Mongolia 29.03 26.24 4.72 8.17 11.63

Ningxia 4.48 3.84 0.52 0.91 1.30

Xinjiang 24.67 20.99 5.56 7.79 10.01

Plateau 2.91 2.38 0.12 0.58 1.04

Tibet 1.12 0.89 0.04 0.21 0.39

Qinghai 1.79 1.49 0.08 0.37 0.66

Central and East 175.27 137.93 41.58 63.90 86.19

Shanghai 1.27 0.97 0.37 0.49 0.61

Jiangsu 39.19 30.54 10.66 15.32 19.97Zhejiang 8.58 6.69 2.63 3.72 4.81

Anhui 40.60 32.08 10.97 15.56 20.15

Hubei 31.82 25.64 7.90 11.76 15.62

Hunan 32.47 25.54 3.81 8.79 13.74

Jiangxi 21.34 16.46 5.25 8.27 11.29

Southwest 86.39 72.20 7.08 24.82 42.59

Chongqing 12.44 10.27 1.94 4.32 6.70

Sichuan 39.44 32.33 1.23 9.59 17.98

Guizhou 13.01 11.10 1.56 4.14 6.71

Yunnan 21.50 18.51 2.35 6.77 11.20

South 59.11 48.57 15.44 22.82 30.20

Fujian 6.86 5.35 0.78 1.60 2.43

Guangdong 17.35 13.93 4.16 6.41 8.66

Guangxi 32.09 27.00 9.42 13.45 17.47

Hainan 2.80 2.28 1.07 1.36 1.64








The amount of crop residues accessible for bioenergy

production would be much lower than the collectable amount

if the alternative uses of crop residues keep their current share

owing to the limited competition power of the emerging bio-

energy industry, as Scenario A assumes. Under Scenario A,

there are only about 147 million tons of crop residues

obtainable at the national level for commercial bioenergy

production, which is about 24% of the total collectable amountor 20% of total theoretical amount. The regional distribution of

the 147 million tons of crop residues is more or less similar to

that of the collectables, but with some variation due to the

differences in the shares of alternative usages across different

regions. For example, Heilongjiang becomes the province with

the highest amount of crop residues accessible for bioenergy

production, and Henan, the number one province in terms of

the collectable, drops to the second place.

The other two scenarios point to the rising competing

power of the new bioenergy industry and highlight that if the

bioenergy sector can grab crop residues from rural conven-

tional fuel use by offering attractive prices, the potential

amount for bioenergy production would be much higher. Forexample, if 50 percent of crop residues currently consumed as

conventional fuel can be taken away by the bioenergy sector

(Scenario B), the total potential amount will increase to 241

million tons, being 63.4 percent higher than the amount

accessible under Scenario A. Moreover, if 100 percent of crop

residues consumed as rural fuel energy can be seized by the

bioenergy sector through direct or indirect price competition

as assumed in Scenario C, the total amount of crop residues

available for bioenergy production will reach 334 million tons,

more than double the quantity obtainable under Scenario A.

4.2. Density of crop residue resource and suitability for

bioenergy plant construction

Economically attainable mobilization of crop residues for

commercial bioenergy production critically depends on thedensity of crop residue output in the neighborhoods of a

favored site. In those neighborhoods with high density of crop

residue output, costs of collection and transportation will be

much lower. With a lower density, bioenergy plant will have

to expand its collection radius to grab minimum amount of

feedstock required by economies of scale to the point at which

marginal cost of grabbing an extra unit of feedstock equals

marginal revenue this unit of feedstock generates. Existing

studies suggest that a 25-km radius is an economically

attainable range for a crop residue based power plant or bio-

energy plant. For example, the studies of both Wang et al. [39]

and Wu et al. [40] show that 24e25 km is the maximum radius

for crop residue based power plant to collect feedstock in aneconomically operational way.

We apply the density calculation method presented in

Section 3 to each 1 1 grid cell if cultivated land accounts for

atleast5 percent ofthe1 km2 area of thegridcellfor Scenarios

A, B, and C, respectively. Fig. 2 reports the density distribution

under Scenario A. It shows that the grid-cells with high den-

sity mostly lies in the three regions of Northeast Plain, Middle

and Lower Reaches of Yangtze River, and Southwest China

Fig. 2 e

Density distribution of crop residue resource availablefor commercial energy productionin ton/km2, under Scenario A.








(mainly, Guangxi province), where majority of the grid cells

have the density of over 100 tons/km2 available for commer-

cial energy production. At the provincial level, there are fourprovinces where majority of grid cells produce more than 200

tons of crop residues per km2, including Henan (>244 t/km2),

Jilin (>231 t/km2), Jiangsu (>224 t/km2), and Guangxi (>223 t/

km2). In contrast, the density in the Loess Plateau and Tibet

Plateau is at the very low end, with an average (across those

crop-related grid cells) of 22 t/km2 and 13 t/km2, respectively.

Figs. 3 and 4 report the density distribution under Sce-

narios B and C. A comparison across Figs.2e4 indicate that the

density disparity extends significantly between provinces at

the high density end and those at the low density end. Henan

in North China, Jilin in Northeast China, Jiangsu in East China,

and Jiangxi, Anhui, Hubei, Hunan in Central China all become

more suitable for crop residue based commercial bioenergyproduction when they move from Scenario A to B and then to

C. In contrast, the potentials in the Loess Plateau and Tibet

Plateau keep very limited under all three scenarios.

As discussed in Section 2.2, the density distribution re-

ported in Figs. 2e4 allows us to further assess the spatial

distribution of suitability for constructing crop residue based

biofuel plants or power plants in different areas. In our

research we consider three radius choices of 25 km, 30 km and

50 km but pay special attention to the 25 km radius for the

following two reasons. First, it is recommended by specialists’

research [39,40], and second, it is in line with the adminis-

trative radius of most counties in the main crop production

regions, which brings administrative convenience given the

well-reported tough inter-jurisdictional competition for eco-

nomic resources across counties and provinces [41]. For the

same reason, we report the results in association with the25 km radius only. Other results are available upon request.

With the currently available technology and within the

radius of 25 km, 47,500 and 180,000 tons of crop residues are

needed for feeding a power plant of 6 MW and 25 MW,

respectively.1 In terms of crop residue based bioethanol plant,

60,000 and 300,000 tons of crop residues are needed forfeeding

an annual capacity of 10,000 and 50,000 tons of bioethanol

production, respectively.2 Fig. 5 presents the suitability dis-

tribution of bioenergy plants with different scales under Sce-

nario A. The figure shows that biofuel plants with an annual

capacity of 50,000 tons bioethanol can be built only in limited

areas of three provinces, i.e., Jilin, Henan, and Jiangsu. Power

plants of more than 25 MW are suitable in areas such asMiddle and Lower Reach of Yangtze River and a limited

number of counties in Northeast Region and scattered small

areas in Guangxi province. In contrast, power plants of 6 MW

Fig. 3 e Density distribution of crop residue resource availablefor commercial energy productionin ton/km2, underScenarioB.

1 According to Wu et al. (2009) [40], unit crop residue conversionrate of a residue-solidification enterprise of 6 MW is 1.1 t/MWh.Assuming an annual operation of 300 days, the quantity of cropresidue needed is 1.1 t/MWh 6 MW 24 300; conversion rateof a residue-solidification power plant of 25 MW is 1 t/MWhand the quantity of crop residue needed is 1.0 t/MWh 25 MW 24 300.

2 According to Song et al. (2010) [1], with the present technologyof ethanol production, unit crop residue conversion rate is 6 tons/

ton.








Fig. 4 e Density distribution of crop residue resource availablefor commercialenergy productionin ton/km2,underScenarioC.

Fig. 5 e

Suitability distribution of bioenergy plants with different scale under Scenario A.








and ethanol plants of 10,000 tons capacity can be constructed

in majority of counties in Northeast, North China Plain, Mid-

dle and Lower Reach of Yangtze River, and Guangxi Province,

as well as in some scatted areas of Xinjiang province.

The suitability pattern improves significantly when the

Scenario moves from A to B and further to C. Fig. 6 presents

the suitability of crop residue based energy plant under Sce-

nario B. Under this scenario, the areas suitable for bioethanolplants of 50,000 tons capacity extend to a large part of Jilin

Province and Middle and Lower Reach of Yangtze River. The

areas suitable for power plants of more than 25 MW capacity

extend to Heilongjiang Province in Northeast, North China

Plain, and majority areas in Middle and Lower Reach of

Yangtze River. Areas suitable for power plants of 6 MW and

ethanol plants of 10,000 tons capacity cover majority counties

of Northeast Region, North China Plain, Middle and Lower

Reach of YangtzeRiver,South China except Fujian, Chongqing

and Chengdu Basin in Sichuan Province.

Fig. 7 shows the suitability of constructing commercial

energy plants with different scales under scenario C. Under

this scenario, the areas suitable for bioethanol plants of 50,000tons capacity extend to the areas suitable for power plants of

more than 25 MW capacity under Scenario B (Fig. 6), and those

suitable for power plants of more than 25 MW capacity extend

beyond the areas suitable for small power plants of 6 MW and

ethanol plants of 10,000 tons capacity under Scenario A. Areas

suitable for power plants of 6 MW and bioethanol plants of

10,000 tons capacity cover almost all eastern and southern

half of China, except a large part of Fujian and some other

scattered (mountainous) areas.

5. Discussion and conclusion

China’s demand for energy has increased rapidly in recent

years and this leads to China’s increased dependence on theinternational energy market. Effectively utilizing crop resi-

dues in commercial energy production is regarded as one of

the key options for the development of renewable energy and

for strengthening energy security in the future. Such recog-

nition has stimulated an increasing number of researches

assessing the quantity of crop residues mobilize-able for

commercial bioenergy production. Most of the existing

studies focus on estimating the total theoretical and collect-

able amounts of crop residues, and pay little attention to the

rising competing power of the emerging bioenergy sector to-

wards the traditional uses of crop residues and the suitability

of constructing bioenergy plants in different areas under a

given density of crop residue resource. This paper fills thisimportant gap by mobilizing up-to-date statistical and

remote-sensing data and by carrying out a geographic and

economic analysis.

Our assessment shows that in 2010 the theoretical amount

of crop residue output in China was 729 million tons and the

collectable quantity was 609 million tons. If the traditional

uses of crop residues keep their current shares owing to the

Fig. 6 e

Suitability distribution of bioenergy plants with different scale under Scenario B.








limited competition power of the emerging bioenergy industry

in the short-run, the amount of crop residues that can be

mobilized for energy production will be about 147 milliontons, accounting for 24 percent of the total collectable

amount. If the buying prices of crop residues by the com-

mercial energy production sector become high enough so that

farmers are willing to sell about 50 percent of crop residues

traditionally consumed for rural fuel energy, the amount of

crop residues for commercial energy production will increase

to 241 million tons or 40 percent of the total collectable

amount. Furthermore, if the buying prices become so high so

that substitutive fuels become much cheaper than crop resi-

dues and farmers no longer use crop residues for heating and

cooking, the amount of crop residues accessible for commer-

cial energy production will furtherincrease to 334 million tons

or 55 percent of the total collectable amount.Constrained by the costs of collection and transportation,

economically feasible utilization of crop residues for com-

mercial energy production depends on the density of crop

residue resources in the neighborhoods of a favored plant site.

In this research we consider a radius of 25 km for crop residue

based energy plants to search the economically suitable sites,

as being recommended by specialists’ researches [39,40] and

being in line with the administrative radius of most counties

in the major crop production regions of China. With the 25 km

radius, our assessment shows that if the traditional uses of

crop residues keep their current shares, bioethanol plants

with an annual capacity of 50,000 tons can be built only in

limited areas of Jilin, Henan, and JiangsuProvinces; and power

plants of more than 25 MW can be built only in Middle and

Lower Reach of Yangtze River and a limited number of

counties in Northeast Region and Guangxi province. If the risein prices leads farmers to sell 50 percent of fuel-energy related

crop residues, a scenario highly plausible in the medium run,

the areas suitable for bioethanol plants of 50,000 tons capacity

will extend to a large part of Jilin Province and Middle and

Lower Reach of Yangtze River; and the areas suitable for

power plants of more than 25 MW will extend to Heilongjiang

in Northeast, North China Plain, and majority areas in Middle

and Lower Reach of Yangtze River. The results also show that

if the price of crop residues offered by the commercial energy

production sector is high enough and attracts all crop residues

away from rural fuel energy use, the suitable areas for bio-

energy plants will be significantly expanded in the east and

southeast regions of China.The findings of this study provide important information to

policy makers in China for formulating plans and policies in

mobilizing crop residues for bioenergy development, also to

commercial companies for the location decisions of their bio-

energy production plants. The Medium- and Long-Term

Development Plan for China’s Renewable Energy [9] puts an

emphasison using cropresidue for power generation and pellet

production. According to this plan, about 300 million tons of

crop residues should be usedfor bioenergyproduction, which is

very close to our estimation under Scenario C. Nevertheless,

this study shows that if the competitive uses of crop residues

and the economic viability of bioenergy plants are considered,

the total quantity of crop residue that can be used for

Fig. 7 e Suitability distribution of bioenergy plants with different scale under Scenario C.








commercial bioenergy production could be much lower. In

terms of the potential role crop residues can play in China’s

total energysupply, we show that even in the two conservative

scenarios of A and B, there will be about 147 and 241 million

tons of crop residues available for commercial bioenergy pro-

duction, which are equivalent to about 73.5 and 120.5 million

tons of standard coal respectively, amounting to 2.5 and 3.8

percent of China’s total energy consumption in 2012.The analysis of this study highlights the importance of

considering the economic viability of a bioenergy plant in

terms of not only collectingand transporting costs but also the

competing power of the bioenergy sector over alternative uses

of crop residues, the latter of which exerts significant impact

on mobilizing crop residues for bioenergy production.

Currently, one of the R&D focuses in the bioenergy production

industry is on how to scale up pilot/demonstration plants to

industrial scales. This study suggests that the R&D efforts

should also pay more attention to networks of small-scale

crop residue-based bioenergy plants because they are more

capable of extending their feedstock bases thus are econom-

ically more viable.

Acknowledgments

The authors gratefully acknowledge the financial support of

Newton International Fellowship of the UK and National Sci-

ence Foundation of China (71073154 and 71222302), and thank

the valuable comments of Christina Prell, Christopher P.

Mitchell (Editor) and two anonymous referees.

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