Reducing nitrogen loss during poultry litter composting using biochar

Poultry litter (PL) is a potentially underused fertilizer because it contains appreciable amounts of N, P, K, and micronutrients. However, treatments like composting to reduce potential pathogens, weed seeds, and odor often result in high losses of N through NH3 volatilization. Biochar (BC) has been shown to act as an absorber of NH3 and water-soluble NH4+ and might therefore reduce losses of N during composting of manure.

We produced three PL compost mixtures that consisted of PL without added BC (BCO), PL + 5% BC (BC5), and PL + 20% BC (BC20). The BC was produced from pine chips and used without further modifications. Three replicates of each treatment were placed in nine bioreactors to undergo composting for 42 d. The entire composting experiment was repeated three times in a complete-block design.

Moisture content, temperature, pH, mass loss, gas (NH3, CO2, H2S) emissions, C, and nutrient contents were measured periodically throughout the experiments. Results showed no difference in PL mass loss with BC addition. Moisture content decreased, pH increased significantly, and peak CO2 and temperatures were significantly higher with BC20 compared with BC0.

These results indicate a faster decomposition of PL if amended with BC. Ammonia concentrations in the emissions were lower by up to 64% if PL was mixed with BC (BC20), and total N losses were reduced by up to 52%. Biochar might be an ideal bulking agent for composting N-rich materials.