Short paper fiber (SPF), a by-product of the paper mill industry, was cocomposted with broiler litter (BL) to determine decomposition rate and NH₃-N loss as functions of C/N ratio and pH of the compost mixes. The SPF generally had a high C/N ratio >200 while the BL, consisting of bedding material (sawdust) and poultry manure, had a low C/N ratio of 10–12. A total of seven series (27 tests) of pilot-scale studies were conducted using two different SPFs mixed with BL. Additives used for pH control were alum (aluminum sulfate), HiClay® Alumina and sulfuric acid. Mixing ratios [SPF/(SPF+BL), kg/kg(dry basis)] used were 0.8 to 0.4. Test conditions were C/N of 17 to 49, pH of 6.6 to 8.3, initial temperatures of −1 to 22°C, composting temperature of 60°C, water content of 50-55% w.b. and remixing two times per week. Composting temperature was controlled using forced ventilation with a high/low fan setting. Composting trials lasted two weeks. Ammonia loss, O₂, CO₂, compost temperatures and dry solids loss were measured. Evaluations of ammonia emissions versus initial C/N and pH showed: (1) NH₃-N loss decreased as initial C/N increased, even above C/N = 38; (2) NH3-N loss decreased rapidly below pH = 7 and increased rapidly for initial pH above 8. Addition of alum and/or sulfuric acid was found to decrease NH₃- N loss while HiClay® Alumina had little or no effect. Results on dry solids loss are not presented in this article.

The feasibility study of potential biogas plants was conducted on a nationwide scale that may be established in each province of Turkey using potentially 10% of all annually collected animal manure. The analysis was carried out using the centralized anaerobic digestion model at thermophilic temperatures. Both equations and data used to calculate the capital and operating cost of biogas plants, as well as combined heat and power system were obtained from the available literature. The production of methane, electrical and heat energy, digestate, revenues, and CO₂ savings due to biogas process were evaluated. The economic viability of biogas plants was evaluated based on the net present value (NPV), benefit-to-cost ratio (B/C ratio), internal rate of return (IRR), and payback period (PBP) based on the inclusion and exclusion of heat revenues at two different electricity purchase prices (0.066 and 0.11 ş/kWh). The results showed that the highest amounts of electrical and heat energy generated were for East Marmara (380.22 GWhe/year and 434.54 GWht/year), respectively, while those of the lowest production were for Istanbul region, 5.25 (GWhe/year), and 6.00 (GWht/year), respectively. The revenues from the produced electrical energy ranged from 0.35 Million Euros per year for Istanbul region to 25.09 Million Euros per year for East Marmara region while the heat revenues from biogas production ranged from 0.20 Million Euros per year for Istanbul region to 14.43 Million Euros per year for East Marmara region. It has been concluded that certain financial mechanisms have to be put into effect, such as increasing market price of electricity produced from biogas plants to give an incentive to biogas producers, as well as fundraising to support construction of biogas plants, and offering both long-term credits and tax breaks for investors.