Composting, anaerobic digestion and biochar production in Ghana. Environmental–economic assessment in the context of voluntary carbon markets

Abstract

In some areas of Sub-Saharan Africa appropriate organic waste management technology could address development issues such as soil degradation, unemployment and energy scarcity, while at the same time reducing emissions of greenhouse gases. This paper investigates the role that carbon markets could have in facilitating the implementation of composting, anaerobic digestion and biochar production, in the city of Tamale, in the North of Ghana. Through a life cycle assessment of implementation scenarios for low-tech, small scale variants of the above mentioned three technologies, the potential contribution they could give to climate change mitigation was assessed. Furthermore an economic assessment was carried out to study their viability and the impact thereon of accessing carbon markets. It was found that substantial climate benefits can be achieved by avoiding landfilling of organic waste, producing electricity and substituting the use of chemical fertilizer. Biochar production could result in a net carbon sequestration. These technologies were however found not to be economically viable without external subsidies, and access to carbon markets at the considered carbon price of 7 EUR/ton of carbon would not change the situation significantly. Carbon markets could help the realization of the considered composting and anaerobic digestion systems only if the carbon price will rise above 75-84 EUR/t of carbon (respectively for anaerobic digestion and composting). Biochar production could achieve large climate benefits and, if approved as a land based climate mitigation mechanism in carbon markets, it would become economically viable at the lower carbon price of 30 EUR/t of carbon.

Thermal Properties of Biochars Derived from Waste Biomass Generated by Agricultural and Forestry Sectors

“…Lignocellulosic biomass is an abundant organic material that, in addition to its use as a fuel, can be upgraded to generate biochar [5]. Biochar is a general term for a solid product derived from the pyrolysis of agricultural or forestry biomass [6,7]. Pyrolysis is a process where a substrate is heated in the absence of oxygen [3], and this conversion is a new strategy to potentially add value to biomass residues [8].…”

“…Depending on its physical and chemical properties, biochar can range from a high-quality fuel [6] to a soil amendment [9]. It may also be used to remediate contaminated soil [10][11][12] or sequester carbon [13,14].…”

Biological response of using municipal solid waste compost in agriculture as fertilizer supplement

“…The composting/vermicomposting of organic wastes involves lower operating costs because of lower capital and technical requirements (Ruggieri et al 2009;Galgani et al 2014). Ruggieri et al (2009) compared external management cost and composting costs of organic fraction of waste generated from wine industries.…”

A kinetic study on how C/N ratio affects energy consumption of composting of rose oil‐processing wastes with caged layer manure and straw

“…Life cycle assessment of composting municipal solid waste was studied by Galgani et al . . Techno‐economic analyses of the composting process of organic wastes in the wine industry were also conducted .…”

“…Kern examined and calculated average energy consumption of 21 kWh ton 21 input material for less mature compost, while average energy required for composting was 30.7 kWh for mature compost production [11]. Life cycle assessment of composting municipal solid waste was studied by Galgani et al [12]. Techno-economic analyses of the composting process of organic wastes in the wine industry were also conducted [13].…”