Could amending different organic wastes with Pulp and Paper Mill Sludge (PPMS) thrive the production performance of Eisenia fetida?

Large quantity (150 Mg/day) of Pulp and Paper Mill Sludge (PPMS) is being generated in Corner Brook Pulp and Paper Limited (CBPPL), Newfoundland, Canada. Since PPMS contains high level of organic matter-OM (80-85%) and moisture content-MC (50-60%), it may be considered for recycling as vermicompost and earthworm as animal feed. An initial attempt on vermicomposting PPMS using Eisenia fetida had a long processing time up to 80-90 days. Therefore, the current study was designed to shorten the processing time by amending PPMS with different organic wastes and monitoring production performance of Eisenia fetida.

Organic wastes - poultry bedding material (SP), vegetable peels (SV), soil (SS), fresh cow manure (SC-L) and composted cow manure (SC-C) were amended separately with PPMS in 2:1 ratio as the treatments while PPMS alone was the control (S). About 14.1-14.5 g of earthworms/ 3.6 kg of substrate (an average stocking density of 4 g/kg) were introduced in all the treatments which were triplicated in completely randomized design. Changes in vermicompost parameters such as pH, electrical conductivity (EC), OM, MC, etc. were monitored weekly and the population dynamics of earthworms were studied, bi-weekly. The MC was maintained at about 75-80% in all the treatments. Results showed that amending organic wastes with PPMS had a significant (p< 0.0001) influence on the quality and quantity of the final vermicompost produced. The total quantity of vermicompost produced was higher (73.8%) in SC-L followed by SV (70.4%), SC-C (69.8%), SS (67.3%), S (64.3%) and SP (8.8%) in 45 -50 days. pH decreased in all the treatments except in control until 30 days and increased afterward to reach the range between 6.1 and 7.3. EC in all the treatments S, SV, SS and SC-L (except SP and SC-C) reduced from the initial value of 2.90, 2.66, 1.23 and 3.18 to 2.58, 2.56, 2.69 and 2.69 mS/cm, respectively. Simultaneously, OM content showed a decline in all the treatments, while the reduction rate was higher in SS (4.71%) > SV (4.02%) > SP (3.94%) > SC-L (2.91%) > SC-C (2.67%) > S (1.81%). Total biomass gain of Eisenia fetida was 56.1%, 40.4%, 22.3% and 13.4% in SC-L, SC-C, SV and SS, respectively in day 45. Conversely, a reduction in earthworm biomass of 55.8% and 60.1% was observed for S and SP, respectively. The average biomass growth rate was higher in SC-L (1.73 g/day) followed by SV (1.35 g/day) and SS (1.22 g/day). As a whole SC-L, SC-C, SV and SS had no significant difference (p> 0.05) among them in both total biomass gain and growth rate while those treatments had the significant difference with S and SP (P< 0.0001). Therefore, we conclude that the PPMS can be an excellent substrate to reuse in vermicomposting. However, incorporating various organic manures and wastes could enhance the vermicomposting rate and significantly reduce the processing time. Further improvements can be achieved by adjusting factors such as the types and ratio of organic wastes, and the number of earthworms involved.

Keywords: Eisenia fetida, PPMS, cow manure, vegetable peels, poultry bedding, soil