Assessment Of The Mitigation Potential Of Greenhouse Gas Emissions For Biochar Technology

Biochar is a carbon-rich, fine-grained and porous product, which is produced bypyrolysis of organic materials under limited supply of oxygen and at relatively lowtemperatures （<700°C）. Because of its potential in soil amelioration and mitigation ofgreenhouse gas （GHG） emissions, biochar has become a hot topic in many researchfields. In this thesis, The potential of biochar technology in mitigating GHG emissionswas assessed. Meanwhile, the energy input and output in biochar production was alsoanalysed. Based on these results, the potential of biochar technology in mitigating thepressure from GHG emissions and improving the energy structure for our country wasinvestigated. Moreover, economics is a fundamental factor for a new technology thatis accepted and widely used in the initial stadges. Therefore, an economic analysis forbiochar’s production and application was conducted. Finally, the prospect ofdevelopment and application of biochar technology in our country was analyzed usingthe SWOT （Abbreviation of four words: Strength, Weakness, Opportunities andThreat） method. The results of this study are hoped to provide a feasible way tomitigate GHG emissions, improve energy structure and provide an effectivetechnology for utilizing the waste biomass resources. In the meanwhile, scientific dataand theoretical support would be provided in development and application of biochartechnology. The main results of this study are as following:（1） The ways of carbon sequestration and GHG abatementusing biochar havebeen explored, including the following aspects: the carbon stored in biochars; theGHG abatement from renewable energy production, which can be alternative forfossil fuel; the carbon sequestration from increased biomass, which may absorb moreCO₂from atmosphere through photosynthesis; the abatement from reduction of soilN2O emissions; the GHG abatement from the reduced demand for synthetic fertilizers;the GHG abatement from suppressing soil organic carbon decomposition.（2） The balances of GHG and energy of biochar technology were quantitativeanalysis using LCA method. The balance of GHG for biochar production from crop residues, forest residues, livestock excrement and municipal organic waste are-829.30,-1105.83,-742.37and^-1953.70kg CO_2e t^-1biomass, respectively, all showthe positive results. For crop residues, forest residues and livestock excrement, thegreatest contribution to carbon abatement is carbon sequestration in biochars, and thenext largestproportionis renewable energy production and fossil fuel offset,agricultural effects of biochar application show a relatively smaller amount. For themunicipal organic waste, the greatest contribution to carbon abatement is reduction ofCH4emission. The net energy production for these four feedstocks are334.06,-512.80,466.12,544.47MJ t^-1biomass, respectively. The forest residues shows anegative result because of the collection stage, which would consume a lot of energy.The main processes of energy input for all feedstocks in biochar technology are theprocesses of biochar application into field, feedstock collection and transport, totallyaccounting for90%of total energy input.（3） Based on the LCA results of biochar carbon abatement and energy production,combining with the survey of the potential in biomass sustainable utilization in ourcountry, the carbon abatement and energy production potential of biochar applicationwas assessed. The total amount of biomass resource for these four feedstocks in Chinaare23.14×10⁸t, and thesustainable utilization potential are14.02×10⁸t. In thisresources background, the total carbon sequestration and abatement are12.70×10⁸t,equivalent to17%of total GHG emissionsin China in2005. The total renewableenergy production are49.50×10¹⁰MJ, equivalent to13.75×10¹⁰kWh. Therefore, itmay conclude that biochar technology has high potential to mitigate China’s GHGemissions and improve the structure of energy supply.（4） The economic feasibility of biochar technology was also explored. Theresults demonstrate that the price of carbon abatement in the carbon trade market andthe cycle of biochar application are the critical factors to the economic feasibility ofbiochar technology. In the context of low carbon abatement price, most of biocharsfrom different materials have a plus production cost, and then farmers employ thebiochar in this scenario will obtain negative economic profits when the applied cycleis lower than ten years. In the contrary, at high carbon abatement price, excluding forest residues biochar, other three biochars may obtain negative production cost, andthen in this scenario farmers employ biochars have positive economic profits in everyapplied cycle. Employing municipal organic waste in biochar production may bring abigger economic potential than any other feedstocks. According to these results, wemay conclude that, with increasing pressure of GHG emissions in future, the carbonabatement price and the economically attractive of biochar technology will increase.Additional, choosing a suitable biochar applied cycle through strengthening thelong-term research also may improve the economic performance of biochartechnology.（5） The prospects of biochar technology in China was also employed usingSWOT analysis method. The results reviewed and assessed the factors of strengths,weaknesses, opportunities, and threats of biochar technology. The strengths of biocharincluded the potential in carbon abatement, agricultural production, renewable energyproduction, inhibiting the pollution from agricultural sources, and high economicattractiveness. Abundant biomass resources in China is also the significant strengthfor biochar technology. The weaknesses of biochar can be listed as follow: the relativelow level of the reliable technology base and research, less funding channels,differences in spatial and temporal distribution of biomass resources, and instability ofthe expected benefits. In addition to the internal factors of biochar technology, theexternal environment also brings opportunities and threats to biochar technology. Thedemand for reducing agricultural sources of greenhouse gas emissions and pollution,easing soil acidification, strengthening renewable energy, reducing the cost ofagricultural production, increasing farmers’ income are the opportunities to biochar.The threats of biochar included: irreversibility of biochar application, lacking ofassessment and certification mechanism of carbon emission reduction, competitionbetween facing biomass energy, backward of related policy research and establishment. The overall studies show that biochar technology has broad prospectsin the development of our country.