Turned windrow composting of cow manure as appropriate technology for zero discharge of mulberry pulp wastewater

Abstract

Turned windrow composting was investigated as appropriate technology for recycling the wastewater (excluding black liquor) from mulberry pulp and paper handicrafts. Two exterior turned windrows (1.5 m width×1.5 m height×2.0 m length) with dry leaves/cow manure/sawdust wet weight ratios of 60:40:0 (Pile A) and 55:40:5 (Pile B) were used for the investigation. Changes in the physical and chemical properties of the compost were examined and a phytotoxicity analysis was performed. A soil incubation test and an informal focus group discussion were also conducted. The results revealed that while both piles met the regulatory processing requirements for further reduced pathogens (≥55°C for 15 days or longer), the operation without sawdust (Pile A) not only significantly enhanced the thermophilic temperature regime (P<0.05) but also yielded the highest amount (1.4 m3 ton−1 pile) of wastewater elimination during the first 2 months of composting. It was found that the constant rates of degradation were 0.006 day−1 (Pile A) and 0.003 day−1 (Pile B), and no pronounced statistically significant difference in N losses was found (P>0.05). The germination index of two plant species in both piles varied between 126% and 230% throughout the experiment, and no pronounced differences (P>0.05) among the samples were found. Addition of the compost significantly improved soil organic matter and pH (7–8), as well as reduced the loss of NO 3-N. Local discussion groups were initiated to evaluate the cost–benefits, the potential of wastewater removal, the cooperation of community users and supporters, the compost quality and the potential compost market.