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Anaerobic Digestion

Numbers (and Alessandro Volta) don’t lie: Anaerobic digestion as a potential solution towards sustainable wastewater re-use and renewable energy for Mexico

Christian Borja-Vega's picture
Example from part of a biogas plant
By Bertold Werkmann via Shutterstock

In one of Mexico City’s most populated areas, Iztapalapa, there is a street named Alessandro Volta. With little knowledge about who this man was, we researched a bit and found that Alessandro Volta concluded, in 1776, that there was “a direct correlation between the amount of decaying organic matter and the amount of flammable gas produced”. Sir Humphry Davy determined 32 years later (in 1808) that methane was present in the gases produced during the anaerobic digestion (AD) of cattle manure. The first digestion plant was built at a leper colony in Bombay, India in 1859 (just 83 years later!).

Anaerobic digestion (AD) as a renewable resource has been growing since, in the international context, and has the potential to be a sustainable, affordable solution for wastewater management. In the 21st century, we are still fascinated with the idea of the benefits of biogas production. In modern times, AD is being used as a reliable energy source, and sludge resulting from AD processes can be used as fertilizer. Countries like the UK are producing enough biogas to power 1 million homes, 210 years after Sir Humphry Davy’s discoveries. In fact, according to a new report from the Anaerobic Digestion & Bioresources Association (ADBA) of the UK, in 2017 the total energy generation from anaerobic digestion plants reached 10.7 Terawatt-Hour (TWh) / year.

A low-priced water reuse process that also delivers renewable energy in rural areas

Christian Borja-Vega's picture

What do Yucatan (Mexico), Michoacan (Mexico), Karur (India), and Jan Kempdorp (South Africa) have in common? These are all places with successful stories of implementing Anaerobic Digestion (AD) for wastewater treatment. But what is AD? What are the benefits?  

AD systems are installed for many different purposes, such as a waste treatment step, a means to reduce odours, a source of additional revenues, or a way to improve public image. The AD treats water and waste, reducing adverse environmental impacts. Through AD, two main by-products can be obtained: biogas—that can be used as a fuel, and sludge—that can be used as a soil amender for improve crops. These AD “by-products” are important in the context of mitigating the impacts of climate change, where environmental co-benefits come from efficient use of “by-products”. For instance, livestock enteric fermentation, livestock waste management, rice cultivation, and agricultural waste burning are all sources of methane emissions, representing between 7 and 10 percent of global methane emissions. AD not only treats water through an environmentally sustainable approach, but also contributes to produce high rates of methane for recovery and further utilization.

Source: The Global Partnership on Output-based Aid, 2015. Note Number 8. Biogas Support Program in Nepal.