Composting Old Bark and Wood Waste in Cold Weather Conditions

Abstract

The pulp and paper industry generates large quantities of bark and wood waste (BWW), most of which is disposed of at bark dumps. There are dozens of such dumpsites in Russia, some of which cause negative environmental impacts due to their proximity to bodies of water. Unlike fresh BWW, old BWW is characterized by significant heterogeneity. Given that BWW stored long-term in bark dumps is a water-heavy woody material subjected to varying degrees of microbiological decomposition, the most acceptable method for its disposal is composting. This text presents the results of studies focused on the process of field composting BWW in heaps with natural aeration during the cold season in the region of Perm, Russia. Composting was carried out in two ways: (1) with mineral fertilizers; (2) with both mineral fertilizers and a microbiological inoculum. Concurrent with the field composting, laboratory composting was carried out under controlled conditions. At the end of a 60-day process of field composting old BWW at ambient temperatures of 5 to −14 °C, there were decreases in the values of the compost mixture: loss on ignition (LOI) fell by 22%, chemical oxygen demand (COD) by 98%, and respiratory activity (AT4) by 32%. In laboratory conditions at an ambient temperature of 30–35 °C, LOI decreased by 24%, COD by 98%, and AT4 by 39%. The introduction of a microbiological inoculum into the compost mixture did not intensify the biochemical destruction process of old BWW, neither in the laboratory nor in field conditions.