The Dynamics of Greenhouse Gas Emission during Food Waste Composting

Lioba Chelangat Ronoh; Machito Mihara; John Bosco Mukundi; Catherine Ngamau; Aggrey Adimo; Narong Touch

doi:10.4314/jagst.v23i4.3

Authors

Lioba Chelangat Ronoh Department of Horticulture and Food Security, School of Agriculture and Environmental Sciences, Jomo Kenyatta University of Agriculture and Technology, Nairobi, Kenya https://orcid.org/0009-0009-6923-7536
Machito Mihara Faculty of Regional Environmental Science, Tokyo University of Agriculture, Tokyo, Japan
John Bosco Mukundi Department of Horticulture and Food Security, School of Agriculture and Environmental Sciences, Jomo Kenyatta University of Agriculture and Technology, Nairobi, Kenya https://orcid.org/0000-0003-4622-2701
Catherine Ngamau Department of Horticulture and Food Security, School of Agriculture and Environmental Sciences, Jomo Kenyatta University of Agriculture and Technology, Nairobi, Kenya https://orcid.org/0009-0009-6923-7536
Aggrey Adimo Department of Horticulture and Food Security, School of Agriculture and Environmental Sciences, Jomo Kenyatta University of Agriculture and Technology, Nairobi, Kenya
Narong Touch Faculty of Regional Environmental Science, Tokyo University of Agriculture, Tokyo, Japan https://orcid.org/0000-0001-7881-7000

DOI:

https://doi.org/10.4314/jagst.v23i4.3

Keywords:

composting, GHG, Cow dung, Food waste

Abstract

Composting is an environmentally friendly method of managing organic waste, but it has a substantial downside in the form of greenhouse gases (GHGs) emissions such as: carbon monoxide (CO), nitrous oxide (N₂O), methane (CH₄), and carbon dioxide (CO₂). Organic waste makes up a total of 67% of total waste released daily in Kenya, while cow dung is a readily available resource. The aim of this study was to assess the dynamics of the emissions of GHGs specifically CH₄ and CO₂ from organic waste in an in-vessel aerated composting system. The feedstock was a mixture of cow dung and food waste materials and was composted for a total of sixty days. Five treatments: T0 = 100% cow dung (CD), T1 = 75% CD + 25% food waste (FW), T2 = 50% CD + 50% FW, T3 = 25% CD + 75% FW and T4 = 100% FW + 0% CD were set up in a complete randomized design (CRD) layout. GHGs emissions were collected using a plastic gas pack from each treatment weekly from the 2^nd week to the 8^th week of the composting process and measured using gas chromatography methods. The GHGs emission gradually reduced as composting progressed. The average carbon dioxide equivalent (CO₂e) for the entire period from treatments T0, T1 and T2 were 1.282, 4.322 and 2.596 kgCO₂e/ton respectively; these were higher compared to, T3: 0.380 and T4: 0.534 kgCO₂e/ton. ANOVA analysis indicated that there were significant differences in GHGs emission between treatments, p<0.05. Tukey’s HSD affirmed that treatments T0, T1 and T2 were significantly different from each other and from treatments T3 and T4. Treatments T3 and T4 were not significantly different from each other. The C:N ratio at end of the decomposition process ranged between 26:9 and 22:9, which is higher compared to the recommended 15:1 for agricultural production. Treatment T3 emitted the least GHGs to the environment, thus, a combination ratio of 25% CD + 75% FW is recommended which is within EPA recommended range of 0.1 to 0.5 kgCO₂e/ton of composted wet waste.