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| 1 |
ID:
111399
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| Publication |
2012.
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| Summary/Abstract |
Biochar is a carbon- and energy-rich porous material produced through slow pyrolysis of biomass, which has been proposed as a way of storing carbon in soils for the long-term (centurial to millennial timescales) but its production incurs an energy penalty. Gasification of rice husks at paddy mills combines the benefits of reasonably efficient delivery of energy with a reasonably high carbon char and ash mixture. The ca. 35% carbon content of the rice husk char is possibly a consequence of the protective shield of silica, preventing full exposure of the biomass to oxidation in the gasifier. In this paper we undertake an evaluation of the sustainability of this 'gasification-biochar system' (GBS) in Cambodia, where a rapid deployment of gasifiers is underway. In Part I, we describe the context and analyse (some of) the physical and chemical properties of the biochar. While there are some potential health, safety and environmental issues that require further analysis, they are problems that could be readily addressed in further research and appear to be resolvable. In Part II, we present results from field trials, summarise the data on the carbon abatement of the gasification-biochar system and present some preliminary economic data.
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| 2 |
ID:
111366
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| Publication |
2012.
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| Summary/Abstract |
In part I we described the gasification technology and characterised the physio-chemical properties and environmental impacts of the rice husk char (RHC) by-product. In part II we present summary results from field trials using the RHC, and provide an estimate of the carbon abatement and economic evaluation of the system. Statistically significant yield increases are demonstrated for RHC addition in irrigated rice cultivation (33% increase in paddy rice yield for a 41.5 t (dry weight) RHC application per hectare). The carbon abatement from the RHC addition is approximately 0.42 t CO2 t-1 rice husk; including energy generation from gasification this increases to ca. 0.86 tCO2 t-1. Assuming a carbon value of $5 t CO2 t-1, and agronomic value of $3 t-1 RHC based on the field trials, the economic value of the RHC varies from $9 t-1 (including only recalcitrant carbon) to $15 t-1 (including avoided emissions from energy production). We summarise results from parts I and II, concluding that the gasification-biochar system meets many of the criteria of sustainability, but requires better waste water management and more field trials to demonstrate repeatable agronomic efficacy of RHC application.
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