Biochar Research for Biorefining

Summary

Georgia faces challenging opportunities in the full spectrum of its economy, in agricultural and industrial sustainability, and climate change mitigation. As we work to develop a Biobased economy and biomass industry to produce biofuels, we must also face potential impacts proactively. Biochar research has proved encouraging as a prospect to improve depleted soil nutrients, and enhance poultry litter as a cost effective and environmentally sustainable fertilizer.

Situation

The opportunities related to biochar are multifaceted. Firstly, as the top-broiler producing state in the country, Georgia is estimated to generate an average of two billion kg poultry litter annually. Because it contains both macro and micronutrients, much of this poultry waste is land-applied to pastures and no-till cropping systems. While this material offers a cheap fertilizer source particularly for nitrogen(N) and phosphorus(P), up to 30% of its N value decreases as this nutrient converts into ammonia (NH3) and readily escapes into the atmosphere. Composting poultry litter before spreading it can reduce potential pathogens like weed seeds and odor, yet it too results in high losses of Nitrogen through ammonia volatilization, thus posing environmental hazards while decreasing its fertilizing efficiency. Secondly, Georgia's intensive land management and warm humid climate have resulted in agricultural and silvicultural soils with low soil organic carbon and depleted fertility, thus compromising our agricultural prosperity and economic stability. Lastly, as we develop biofuel technologies, removal of crop residues or collection of biomass reduces the soil organic carbon (SOC) and negatively effects soil productivity.

Response

UGA's Biorefining research team is addressing all of these concerns through concentrated research of Biochar, a by-product of biofuel production. Researchers are developing a way of improving the effect of poultry litter as fertilizer, or maximizing the composting process, by mixing it with biochar. Similarly, it has been found that pyrolysis of crop residues for bioenergy production and the redistribution of the resulting biochar is a highly efficient way to mitigate the potentially harmful effects thereof, by increasing the soil nutrients and sequestering carbon.

Impact

UGA's research has shown a potential way of minimizing ammonia (NH3) loss from poultry litter by mixing it with biochar. Biochar, a by-product from bio-fuel production, exhibits cation exchange behavior. When acidified, this highly porous substance may reduce NH3 emission from the litter, thus helping to curtain harmful environmental pollution. Considering this potential to minimize NH3 loss, however, its effect on litter decomposition and release of inorganic N and phosphorus (P) are areas which also need to be investigated. Studies to evaluate the effect of char on NH3 volatilization, CO2 evolution, and release of inorganic N and P from surface-applied or incorporated poultry litter are ongoing. In regards to the composting of poultry litter, UGA is conducting studies to evaluate the effect of char on ammonia (NH3) volatilization, CO2 evolution, and release of inorganic N and P from surface-applied or incorporated poultry litter. Biochar has been shown to act as an absorber of both NH3 and water-soluble ammonium (NH4+) and might therefore reduce losses of N during composting of manure. These results indicate a faster decomposition of PL if amended with biochar. Ammonia concentrations in the emissions were lower by up to 64% if PL was mixed with biochar (BC20) and total N losses were reduced by up to 52%. This research indicates Biochar to be an ideal bulking agent for composing N rich materials. Research also includes thermochemical conversion (pyrolysis) as an option to process poultry litter to renewable energy (synthesis gas and hydrocarbon fuels) and biochar. In comparison to common biological treatments such as composting, pyrolysis of poultry litter is faster, more compact, and destroys potential pathogens and most pharmaceutically active compounds. During the pyrolysis process important plant nutrients (P, K, Ca, and Mg) concentrate in biochar (Gaskin et al. 2008), but depending on pyrolysis temperature, nutrients susceptible to volatilization such as N are partially lost during the process. Consequently, pyrolysis may reduce the costs associated with land application and transportation, but may also decrease the value of the litter, because most farmers rely on it for nitrogen. The concentration of P also raises concerns about proper management because high P levels in poultry litter have been associated with water quality problems. In comparison to common biological treatments such as composting, pyrolysis of poultry litter is faster, more compact, and destroys potential pathogens and most pharmaceutically active compounds, and warrants further research. Recent research on biochar as a soil amendment has shown beneficial effects on soil fertility apart from its nutrient content, and received attention as potential sink for atmospheric CO2, or sequestering carbon, due to the biochar's recalcitrance against decomposition. However this recalcitrance seems to have implications to nutrient availability; further research is ongoing. Research is being conducted to determine the efficacy of pyrolysis of crop residues for bio-energy generation coupled with the redistribution of the resulting biochar. Our research shows biochars from different feedstocks vary in nutrient content and carbon to nitrogen ratios (Gaskin et al., 2008) and this may affect carbon mineralization rates and nitrogen availability. During the pyrolysis process, important plant nutrients (P, K, Ca, and Mg) concentrate in biochar (Gaskin et al. 2008) and specific studies are evaluating which biochars, peanut hull and pine chip, are most effective, and how different pyrolysis methods can affect nutrient content.

State Issue

Agricultural Profitability and Sustainability

Details

• Year: 2009
• Geographic Scope: State
• County: Clarke
• Program Areas:
  • Agriculture & Natural Resources