Technologies, challenges and perspectives of biogas production within an agricultural context. The case of China and Africa

Abstract

The use of fossil fuels in modern economies has been a success because of the low cost of fossil resources. However, the depletion of fossil reserves, the increase in waste production and global warming concerns have led to increased research on the production of biofuels from renewable resources. Waste production is steadily increasing in quantity and constantly changing in quality, creating enormous risks for the environment and, consequently, for the health of the population. This situation is much more worrying in developing countries, in particular because of the considerable delay in the field of the conversion and recovery of biomaterials, due to their difficulty in approaching the problem in a way that fits their context. The composition of such wastes and residues, rich in organic matter, allows their conversion via biochemical mechanisms, thus constituting an effective solution to address the environmental problems of their disposal. Anaerobic digestion remains a valuable and effective technology for transforming these biomaterials into biogas. The present review focuses on technologies, challenges and areas of application of biogas, especially in China and some African countries, in order to promote the large-scale use of biogas for electricity generation and biofuels. Results point out that China is more used to this technology, while African countries still rely on traditional and less advanced technologies, thus hampering the potential derived from the large availability of biomaterials. Both realities, however, share similar backgrounds about the dimension of the biogas plants and their non-commercial purposes, even if China is recently shifting toward the adoption of a different model. These considerations are used in the article to open an interesting new scenario of political alternatives which may provide a way out from poverty and economic dependence, within the framework of a wider circularity.

Energy Production from Biodegradable Waste as an Example of the Circular Economy

“…Methane is such a gas as well. Although produced in natural processes, it is more harmful to the environment because it is 25 times as potent as CO 2 [9]. Methane is released from hard coal deposits during the extraction of that resource [10]; it is also produced as a result of anaerobic fermentation of organic matter generated during food production and processing as well as municipal waste management.…”

Energy Self-Sufficient Livestock Farm as the Example of Agricultural Hybrid Off-Grid System

“…Methane emitted in natural processes has a negative impact on the environment as it has a carbon dioxide equivalent of 25 times. Methane emissions can be reduced by fermenting the organic matter in biogas plants [1]. Biogas is a mixture of methane (40-85%), carbon dioxide (16-48%), and other gases present in trace amounts.…”

“…As a result of the fermentation of organic material, clean and cheap fuel in the form of biogas is produced. It can be used for heating, lighting, and powering machines [1]. Fermentation, however, is an unstable process as it may be disturbed by an increase in temperature in a fermentation chamber, overproduction of volatile fatty acids, and chemical contamination, e.g., with pesticides or heavy metals [4].…”

“…In Asian [2,6,12,13] and African [1,2,6] countries, small household biogas plants, in which animal droppings are used as substrate, are popular. The fermented substrate (digestate) is transported to the fields as fertilizer with a high nutrient content [14].…”

“…Electricity and heat are used locally, or fed into the grid [15,16]. Purified biogas is used to power cars, buses, and trucks [1].…”