Abstract
A shift from a linear economy to a circular economy of resource consumption is vital for diverting the value from lost resources to resource-efficient products towards developing a sustainable system. Household digesters provide one opportunity to create a biogas-based circular economy. Because household digesters are typically fed a wide and variable range of substrates, it is important to determine the ideal mixing ratios for them. In this study, an anaerobic digester startup process was analyzed and an assessment of anaerobic co-digestion of food waste with different livestock manures was carried out at ambient temperatures. Food waste (FW), cow manure (CM), poultry litter (PL) and goat manure (GM) were co-digested at mixing ratios (FW:PL:CM) of 2:1:1, 2:2:1, 1:1:2, 1:1:1 (wt/wt) and FW:PL:GM at mixing ratios of 2:1:1 and 1:1:2, at an organic loading rate of 1 g volatile solid (VS)/L/day, and 8% total solids. A maximum methane yield was obtained from co-digestion of FW:PL:GM at a mixing ratio of 2:1:1 in autumn-to-winter conditions, 21–10 °C, while the mixing ratio of FW:PL:CM at 2:2:1, showed negligible methane production under the same temperature condition. This study suggests that co-digestion of food waste and poultry litter with goat manure yields more biogas than other substrate combinations. Therefore, selecting suitable co-substrates with an optimized mixing ratio can promote several key indicators of a biogas-based circular economy towards achieving sustainable development goals 2, 3, 5, 6, 7, 9, 13 and 15.
Highlights
Accepted: 9 March 2022About 28 percent of the world’s agricultural land area and 250 km3 of total water volume are used annually to produce food that is lost or wasted [1]
1.3 billion tons of food waste consisting of vegetables, cereals, dairy products, fruits, and meat is wasted or lost globally A significant amount of food is lost during the early and middle stages of our food supply chain, whereas much less food is wasted at the consumer level
Organization (FAO) of the United Nations, the greatest greenhouse gases (GHGs) emission reduction potential from ruminants could be achieved from Southeast Asia and Africa. It claims that GHG from livestock could be reduced by 30% if existing technologies like anaerobic digestion are widely practiced in these areas [7,8]
Summary
About 28 percent of the world’s agricultural land area and 250 km of total water volume are used annually to produce food that is lost or wasted [1]. In South and Southeast Asia, only 6–11 kg of food per capita per year is wasted due to consumers’ purchasing or eating habits or due to oversupply of food in the market. 120–170 kg is lost per capita each year due to poor infrastructure, lack of technology, and inefficiency in the food supply chain. The average municipal solid waste (MSW) generation in Nepal is estimated to be about 0.32 kg/capita/day, of which. 60% is constituted of organic waste [3]. The total organic waste from municipalities of
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