Monitoring the changes in some physicochemical components of compost from peat, dewatered pig manure and fly ash on a scale of (3-5) tons/batch

Abstract

   The presence of fly ash at the concentration of 25% in compost containing peat and dewatered pig manure altered some physicochemical properties of the compost in batches ranging from (3 to 5) tons of raw materials, leading to an extended mesophilic phase, as compared to conventional composts. During the mesophilic phase, the temperature was maintained at (50-55) °C for 10 days, while the pH decreased from 7 to 5.5. In the ripening (stabilization) phase, the temperature dropped to 40 °C after 28 days, and a neutral pH (6.5-6.8) was observed. The mineralization process reduced the organic carbon content from 16.23% to 13.06%, while total nitrogen (N), total phosphorus (P), and total potassium (K) levels increased from 0.83% to 1.27%, from 1.06% to 1.38%, and from 1.38% to 1.8%, respectively, thereby reducing the C/N ratio from 19.53 to 10.28. Through the mineralization process, nutrients were converted into simpler, inorganic (mineral) forms that plants can readily absorb, including available phosphorus (P_avail) and potassium (K_avail). During the ripening stage, the addition of nitrogen-fixing and phosphorus-decomposing bacteria increased the availability of nitrogen and phosphorus. A stable, mature compost was obtained after six weeks.