Composting high moisture materials: Biodrying poultry manure in a sequentially fed reactor

A pilot-scale composting reactor was developed, manufactured, and tested to enhance the biologically heated drying of high-moisture ingredients while minimizing bulking amendment requirements. This biodryer consists of two horizontal cylindrical chambers with internal augers for mixing, materials transport, and aeration. Three tests were run using poultry manure as a feedstock, once without and twice with sawdust amendment. Manure was added to the biodryer sequentially, every other day during each 6-day experimental period. Moisture content, temperature, NH₃ and H₂S emissions, nitrogen, phosphorus, potassium, calcium, and seedling germination rate were analyzed throughout the experimental period. Results indicated that while sawdust was required to maintain aerobic conditions, sequential feeding was effective in reducing the amendment requirements by recycling the amendment through multiple batches of manure. Cumulative sawdust:manure volume ratios were reduced from 2.5:1 in the initial mixtures to 1:1 or less after two additions of manure. For the final trial with bulking amendment, the total VS removal rate was 16% of input VS over the 6-day experimental period, while moisture removal was 51% of the total feedstock water content. The fraction of energy used for evaporation was approximately 44%, with most of the remainder attributed to convective and conductive losses. Additional trials with full-scale, well insulated systems should result in increased moisture removal efficiency.