Potential Production of biomethane and Green Hydrogen from Municipal Waste in Cape Coast, Ghana, for injection into the Ghana natural Gas Grid

Abstract

Biomethane and hydrogen have emerged as promising elements in the transition towards sustainable energy, gaining significant attention due to their capacity to mitigate greenhouse gas emissions and foster sustainable development. In Ghana, efforts to promote sustainable waste valorization for energy production are underway; however, the focus on converting organic waste into biomethane for injection into the natural gas grid still needs to be expanded. This study aims to evaluate the potential of producing biomethane and biohydrogen from the food waste fraction of Municipal Solid Waste in Cape Coast, Ghana for injection of these renewable gases into the national gas grid. The process involves generating biomethane by upgrading biogas produced from anaerobic digestion of food waste. The quantity of biomethane was determined using the modified Buswell equation, incorporating the ultimate analysis of food waste obtained from reliable literature sources. Additionally, hydrogen potential is estimated using the stoichiometric chemical equation for the steam reformation of biomethane. Two scenarios are considered to evaluate the environmental impact: one employing renewable energy-generated hydrogen for methanation and the other using hydrogen derived from steam methane reforming. The results indicate that Cape Coast produced 6.4 thousand tons of food waste in 2021, with projections to 11 thousand tons by 2050 due to linear population growth of 2% according to the World Bank Group. As a result, Cape Coast possesses significant methane and hydrogen production potential, estimated to be 3.7 million m3 and 784 thousand kg in 2021 and projected to reach 6.6 million m3 and 1.4 million kg by 2050. The biomethane potential obtained is equivalent to 0.134 trillion Btu of natural gas as of 2021. This displaces 0.7% of the gas import through the West African Gas Pipeline. Comparing the two scenarios, it is evident that using renewable electricity for methanation leads to lower emissions than employing hydrogen from steam methane reforming. This finding highlights the environmental advantages of integrating renewable energy sources into the biomethane and hydrogen production processes. Converting food waste into biomethane and hydrogen is a viable and eco-friendly method of managing waste in Ghana. This approach not only facilitates the country's transition towards renewable energy but also promotes circular economy principles. Policymakers can leverage these findings to encourage waste-to-energy projects and integrate circular economy strategies into the national energy policy.