Converting Municipal Organic Waste to Biochar for Environmental ...

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dumped at landfill sites and cause environmental problems. Besides, application of untreated organic wastes into soil is an unsustainable practice. However ...
Returning Life to Soil: Converting Municipal Organic Waste to Biochar for Environmental Management and Sustainable Agriculture Mahmudul Islam Piash Department of Soil, Water and Environment, University of Dhaka, Dhaka- 1000, Bangladesh.

Abstract The basic idea is to return the carbon and nutrients back into earth from where they were originally generated and are usually considered as waste. Daily, vast amount of municipal organic wastes are produced throughout the world. These are normally dumped at landfill sites and cause environmental problems. Besides, application of untreated organic wastes into soil is an unsustainable practice. However, proper modification could convert these to a potential soil amendment. These demand a unique technique of bio-resources management that would sequester carbon and nutrients in soil for years to come and ensure quality food production. Therefore, producing Biochar (thermo-chemical conversion of Biomass) from municipal organic wastes might be a reasonable option for hazard-free waste management. Aside from this, incorporation of Biochar improves physicochemical properties of soil, supplies adequate macro and micro nutrients, and reduces the agricultural emission of greenhouse gasses.

Introduction The two biggest challenges of this century are to combat with the changing climate and sustain food production for increasing number of population. To increase agricultural production, soils must be kept healthy. Organic matters are considered as the life of soil which potentially helps to sustain food production. But the climatic condition and existing management practices of our country don’t allow organic matter to be sequestered in soil for long. Moreover, unavailability of adequate biomass makes the addition of organic matter rather difficult. Carbon stored in Biochars can also be sequestered in soil for hundreds to even thousands of years (Preston and Schmidt, 2006), otherwise that would eventually return to atmosphere by natural decomposition. The idea is supposed to solve two major problems of the country. Those are: Increasing amount of municipal wastes (22.4 million tons/year) in major cities and consecutive environmental issues caused by leachate and greenhouse gas emission from landfills (Waste, 2012). Growing threat towards existing food security due to climate change, reduced arable lands, soil degradation, scarcity of water, salinity intrusion and agricultural mismanagement.

Benefits of Municipal organic waste Derived Biochar

Idea Demonstration

The benefits are two folds: better waste management and improved productivity. Waste management benefits If proper management approach can be taken, these wastes would be converted to revenue generating source to waste managing authority (City corporations). Appropriate approach would reduce the need of the waste dumping sites, lower the spreading of hazardous leachate, produce energy, reduce the emission of GHG's from landfills etc. Fig. 2: Demonstration of the Idea

Steps to Idea Implementation Raw material separation Two methods could be utilized for separation of municipal organic wastes. One is the source separation at production facilities; widely used in developed countries. The other one is the separation at disposal sites which is currently more suitable for Bangladesh. The largest landfill site of Bangladesh at Matuail in cooperation with JICA is expecting to use a new waste separation technique (Refuge Derived Fuel- RDF) to separate organic and utilizable wastes from bulk mass. That would facilitate trouble-free collection of biomass for Biochar production at dumping stations. The following diagram shows a demonstration of RDF seperation technique.

Fig. 6: Waste managing benefits (Source: www.ngi.no)

Soil amendment benefits When applied to soil, Biochar adds the fuel for biological life processes. It also improves water holding capacity, raises pH, CEC, specific surface area etc. Moreover, it’s a source of essential nutrients specially the micro’s. A comparative study on Biochars produced from different feedstocks showed unique porosity and Domestic organic waste derived Biochar’s highest nutrient status.

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Fig. 3: RDF separation method (Source: Pyrocrat) Biochar production Biochar production is fully scalable. Pyrolysis ovens are becoming available in all sizes, mobile and stationary: from cooking stoves to industrial-sized units for power generation.

What is Biochar? Biochar is simply defined as a carbon rich by-product obtained by thermo-chemical conversion of biomass in oxygen limited condition for C sequestration or agricultural or environmental management purpose.

Fig. 7: Nutrient content & SEM images of Biochar (Piash et al., 2016)

Limitations of Biochar The major limitation in Biochar production is the unavailability of biomass and energy-requiring production technology. Sometimes, Biochars might contain pollutants if the feedstocks weren’t carefully selected. Moreover, Biochars when applied for the first time, can reduce yield.

Conclusion Fig. 4: Process flow diagram of Biochar Production (Source: International Biochar Initiative)

A full scale commercial Biochar production unit may look like the following unit. Setting up a industrial pyrolyzer at dumping stations might be effective.

A little effort to incinerate biomasses in a partially closed chamber would produce Biochar that can mitigate many problems. Production of Biochar from municipal organic wastes would facilitate one of the best waste management practices, ensure Bangladesh’s contribution to mitigate climate change and enhance soil productivity in a sustainable way.

References 1.

Fig. 1: Terra Preta (Source :www.mavitecgreenenergy.com)

Historical Background of Biochar : The idea of Biochar is a bit old. It was used as a soil amendment for at least 2000 years ago by ancient tribes in the Amazon basin called Terra Petra (Glaser et al., 2002).

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Fig. 5: A commercial Pyrolyzer (Source: dglikes.wordpress.com)

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Glaser, B., J. Lehmann and W. Zech. 2002. Ameliorating physical and chemical properties of highly weathered soils in the tropics with charcoalA review. Biol. Fertil. Soils. 35: 219-230. Piash, M. I., M. F. Hossain and Z. Parveen. 2016. Physicochemical properties and nutrient content of some slow pyrolysis biochars produced from different feedstocks. Bangladesh J. Sci. Res. 29(2): 111-122. Preston, C. M. and M. W. I. Schmidt. 2006. Black (pyrogenic) carbon: A synthesis of current knowledge and uncertainties with special consideration of boreal regions. Biogeosciences. 3: 397-420. Waste Atlas. 2012. Country Data: Bangladesh.