A CLOSED-LOOP BIOCONVERSION SYSTEM FOR CANESUGAR...

A CLOSED-LOOP BIOCONVERSION SYSTEM FOR CANESUGAR INDUSTRY SOLID WASTES TO ENERGY

FOR A SUSTAINABLE SOLUTION

Avijit Dasgupta Ph.D. P.E.Vice President

Enviro Associates International, USA

2018 Waste to Energy ConferenceNovember 29-30, 2018

New Delhi

Background

• Bagasse is the fibrous residue of the sugarcane stocks

• Cachaza is the lime-filter mud from the refining process

© EnviroAssociates International 2017

Background

Every 1000 tons of sugarcane processed produces

• 100 tons of sugar• 270 tons of bagasse waste• 35 tons of cachaza waste


Current PracticeBagasse and cachaza are disposed offsite in open waste piles causing:• Leachate contamination of groundwater• Runoff causing land and surface water contamination of lakes

and rivers• Greenhouse gas emissions from biodegradation in waste piles• Rodent infestation in areas around the waste piles


Current Practice• Burning of sugarcane stocks and leaves

- Air pollution from smoke and particulates

• Burning of bagasse as boiler fuel- Air pollution from particulates and toxic chemicals

emission due to burning of bagasse in mill boilers


Sugarcane Production in India


Major Sugar Production Worldwide

Brazil India China

Sugarcane 650 mill T 300 mill T 120 mill T

Sugar 65 mill T 30 mill T 12 mill T

Bagasse 175 mill T 80 mill T 32 mill T

Cachaza 22 mill T 10 mill T 4 mill T


Problems in sugar industry

• High cost of mill operation (energy) • High cost of sugarcane• Highly competitive market price• Cost of pollution control measures• Cost of waste disposal• Solid wastes (bagasse and cachaza) being

disposed or burned without beneficial reuse


Objective of Study

Find an alternative new approach to utilize the waste bagasse and cachaza to:

1. Prevent pollution2. Recover energy through anaerobic

digestion to reduce operating cost of sugar mills

Clean Environment = Economic Sustainability


Anaerobic Digestion System

Methane gasSugar Mill

Anaerobic Digester

Sugarcane

Sugar

Filter cakeFiltrate

Bagasse & CachazaWastes

Digestate

Sugarcane Plantation

Vacuum Filter


BoilerSteam and Heat

Key Waste Characteristics

Bagasse (%) Cachaza (%)

Cellulose & Hemicellulose

70 10

Lignin 20 2


Challenge: Lignocellulosic Substrate

• Suitable conditions to weaken the bond between lignin and cellulose

• Making the micro organisms to efficiently breakdown the complex substrate to generate methane gas

Lignin is the barrier to access the cellulose for microbial

degradation.


Methodology

• Laboratory-scale digesters were used to investigate feasibility of anaerobic digestion of the bagasse-cachaza mixed substrate

• Two bagasse-cachaza mix ratios were investigated:

1. With 100% bagasse being wasted plus cachaza. Mix ratio bagasse:cachaza 8:1

2. With part of the bagasse burned as fuel in mill boilers. Mix ratio bagasse:cachaza 2.4:1


Process Conditions Investigated

• A. Batch studies• B. Semi-continuous digester studies

- Effect of organic loading- Effect of filtrate recirculation- Effect of detention time- Effect of substrate composition- Effect on gas composition


Batch Studies

• Batch study results indicated that an acclimated mixed microbial culture can breakdown the lignocellulosic substrate to produce methane gas by anaerobic pathway

• Semi-continuous digestion investigation were carried out based on batch study results


Effect of Organic Loading


Effect of recirculation of filtrate


Effect of recirculation on pH


Effect of substrate composition


Effect on Gas Production

Cellulose powder Bagasse-Cachaza Mix

Gas Yield (L/gm of solids) 0.41 0.29

Gas Yield (cu.ft./lb of solids)

6.6 4.6

Volatile Solids Reduction (%)

47.4 37.6


Effect on gas composition

Gas Composition

%

Cellulose

T302 g/L/d

Bagasse-Cachaza Mix 8:1 Bagasse-Cachaza Mix 2.4:1

T10 T30 T10 T30

1g/L/d

2g/L/d

1g/L/d

2g/L/d

1g/L/d

2g/L/d

1g/L/d

2g/L/d

CH478.6 61.8 63.1 68.4 71.7 64.6 65.1 72.9 73.8

CO221.4 38.2 36.9 31.6 28.3 35.4 34.9 27.1 26.2


Closed loop Anaerobic Digestion system

Methane gas1.3 mill cu.ft.(900 mill BTU)Sugar Mill

Anaerobic Digester

Sugarcane1000 T/d

Sugar100 T

Filter cake36 TFiltrate

4 T

Bagasse & Cachaza

149 T

Digestate40 T

Sugarcane Plantation

Fertilizer Vacuum Filter


Boiler

Generator

Electric Power 9 MW

Potential Benefits for Sugar Mills in India

Item Quantity/yr

Sugarcane Production 300 mill T

Sugar 30 mill T

Bagasse 80 mill T

Cachaza 10 mill T

Beneficial Reuse of bagasse (Paper, Fuel) 16 mill T

Gas for Heat, Steam, and Power in Sugar Mills

317,000 mill cu.ft.

Heat for reuse in sugar mills 2220 x 1011 BTU

Electric Power for use in sugar mills and grid

5940 MW

Fertilizer supplement 10 mill T© EnviroAssociates International 2017

Conclusions

• Developed microbial culture was successful in producing methane gas by anaerobic digestion of bagasse-cachaza mixed substrate at mesophilic condition

• 4 cu.ft. of gas was produced per pound of volatile solids added in the digestion process

• Gas produced was rich in methane (70%). No hydrogen sulfide

• A closed-loop anaerobic digestion system was developed with zero waste discharge


Benefits• Closed loop anaerobic digestion system with zero

waste discharge• Beneficial reuse of waste as a resource for clean energy• Methane rich gas produced can be used in the sugar

mill as clean efficient boiler fuel for source of heat energy to lower operating cost

• Use methane gas to run gas turbines to generate electricity

• Reduce fossil fuel use and greenhouse gas emissions• Utilize digester filter cake as fertilizer supplement• Achieves pollution abatement of land, water and air


A clean sugarcane industry environment with bagasse to methane as biofuel offers opportunity for economic growth and sustainable development.


Questions

Thank You

Avijit DasguptaVice PresidentEnviro Associates International

631-241-2860 (USA)9831019908 (INDIA)[email protected]


mailto:[email protected]

A CLOSED-LOOP BIOCONVERSION SYSTEM FOR CANESUGAR...

Documents

Transcript of A CLOSED-LOOP BIOCONVERSION SYSTEM FOR CANESUGAR...