Anaerobic digestion is booming, green gas is going global
As governments around the world recognise the scale of the climate crisis and acknowledge the need for action to counter and mitigate the effects of rising temperatures, anaerobic digestion (AD) is one technology that has enormous untapped potential and is seeing remarkable growth. Something that the inaugural edition of Bioenergy International’s Digital Biogas Special highlights in a compilation of articles that have captured the imagination in terms of good practice, novelty and potential.
A recent report by the World Biogas Association (WBA) illustrates the contribution that anaerobic digestion (AD) can make to meeting the Paris Agreement commitments, and its potential to become a key player in the development of a sustainable circular economy.
A key finding of the WBA report, ‘Global Potential of Biogas’ is that AD technology, which produces biogas from the treatment of wastes, can help reduce global greenhouse gas (GHG) emissions by 3 290 to 4 360 million tonnes CO2 eq or approximately 10-13 percent of the world’s current GHG emissions.
Addressing urban food waste- and wastewater treatment
Furthermore, the report finds that only 2 percent of the feedstocks available are treated through AD. These include food waste, sewage waste, farm waste and crops, which can all be used to make biogas in every country.
Indeed, an estimated 80 percent of all global wastewater discharged is currently not being recycled through an AD process suggesting that there is still a huge potential for governments, city- and urban administrations to address wastewater treatment and curb methane emissions while improving air- and water quality, nutrient recovery and produce biogas as an energy source, displacing fossil fuels.
The use of untreated wastewater from cities to irrigate crops downstream is 50 percent more widespread than previously thought, 65 percent of all irrigated areas within 40 km downstream of urban centers – amounting to about 35.9 million hectares (about the size of Germany) – are affected by wastewater flows to a large degree.
Of the total area of 35.9 million hectares, 29.3 million hectares are in countries with very limited wastewater treatment, exposing 885 million urban consumers as well as farmers and food vendors to serious health risks according to the study ‘A global, spatially-explicit assessment of irrigated croplands influenced by urban wastewater flows’.
Another recent report, ‘Global Food Waste Management: An Implementation Guide for Cities’, also by the WBA in partnership with the C40 Cities Climate Leadership Group Food, Water and Waste Programme puts particular emphasis on the importance of separately collecting and treating inedible food waste.
A “how to do” guide for cities, the report highlights the role of biogas technologies, which through AD recycle inedible food waste into renewable heat and power, clean transport fuel, and nutrient-rich biofertiliser.
AD technologies, which are mature, ready-to-implement, and cost-effective, allow maximum recovery of resources for both green energy generation and soil restoration.
Most cities around the world currently do not collect food waste separately, leaving it to be disposed of in landfills or, at best, in waste-to-energy (WTE) or energy recovery facilities. As a result, food waste is not treated and loses its potential to resolve a series of environmental issues faced by all cities.
A timely guide, given that the ‘Global Gas Report 2018’, jointly published by Snam, International Gas Union (IGU) and the Boston Consulting Group (BSG) estimates that more than 90 percent of global gas’ consumption growth to 2040 will come from cities.
Early-stage for biomethane
On biomethane (aka green gas or renewable natural gas – RNG), the joint report suggests that it is still at “an early stage of development”, although biogas plants have seen strong growth in Europe, driven by favourable policy environments in certain countries.
Renewable gas used in existing gas infrastructure could play an important role in reducing Europe’s greenhouse gas (GHG) emissions to net-zero by mid-century, according to a study conducted by Ecofys and commissioned by the Gas for Climate initiative.
Such a reduction is needed to comply with the Paris Agreement to keep global warming well below 2°C and could save Europe EUR 138 billion annually the study suggests.
Initiated mid-2017, the Gas for Climate group consists of seven leading European gas transmission companies; Enagás, Fluxys Belgium, Gasunie, GRTgaz, Open Grid Europe, Snam and TIGF and two renewable gas industry associations, the European Biogas Association (EBA) and Consorzio Italiano Biogas (CIB).
The study, ‘Gas for Climate: How gas can help to achieve the Paris Agreement target in an affordable way’ shows that it is possible to scale up renewable gas production between now and 2050 to more than 120 billion m3 (bcm) annually, including both renewable hydrogen (H2) and biomethane.
This, the study suggests, is possible through the large-scale implementation of sustainable biomethane production produced from a range of agricultural and woody biomass types.
A “prudent estimation of a truly sustainable” production potential of biomethane within the EU shows that it is possible to produce at least 98 bcm, or 1 072 TWh of energy, annually by 2050.
The study highlights an additional potential to produce 24 bcm of renewable hydrogen by converting low-cost wind and solar electricity into hydrogen. Using this renewable gas in existing gas infrastructure for the heating of buildings, to produce dispatchable electricity as a complement to wind and solar, and to fuel heavy transport, could save about EUR 138 billion annually by 2050 compared to a future energy system without any gas.
In Europe, biomethane use is spreading across the continent. There are now nineteen European producing countries, whose output totalled nearly 2 bcm in 2017. Across the Atlantic, the United States (US) is now the world leader for the use of biomethane as vehicle fuel, further to its production surge of 2014-2017 and driven by federal and state regulations.
The fact that China and India have recently adopted biogas upgrading technology promises to be a game-changer. Both countries have set ambitious biomethane production targets and figures as huge emerging markets. In Central and South America, Brazil is taking regulatory steps to exploit its huge potential.
Clean cooking fuel
It should also be emphasized that biogas and AD technologies can play an important role on a household level for instance as a self-produced source of renewable clean cooking fuel.
In many developing countries, biogas cooking can also improve the livelihoods of rural households, as by-products of biogas production such as slurry and fertiliser boost agricultural productivity.
Modern biogas use, meanwhile, reduces the amount of time spent by women and children collecting fuelwood or saves money by not having to buy fuel such as charcoal, kerosene or liquefied petroleum gas (LPG).
Biogas is also one potential solution to combat household air pollution – according to the World Bioenergy Association (WBA), over 3 billion people worldwide currently use traditional cookstoves (TCS) fuelled by solid fuels such as fuelwood, charcoal or dried manure. These generate considerable indoor air pollution causing serious health and environmental problems.
Despite these clear advantages, the potential of domestic biogas has not been fully exploited.
A technology brief, ‘Biogas for Domestic Cooking’ from the International Renewable Energy Agency (IRENA) provides technical background information, analyses market potential, and barriers, and offers insights for policymakers on biogas for domestic cooking.
Recent research by the US Stockholm Environment Institute (SEI) and Hivos evaluating the performance of the Africa Biogas Partnership Programme (ABPP) of its biodigester market creation efforts in East Africa finds that biogas is a feasible and scalable means of promoting clean cooking and household air pollution reduction in rural Sub-Saharan Africa, though not without adoption challenges especially related to financing.
Thus, in summary, the potential for growth for anaerobic digestion (AD) technologies – from rural household biodigesters to large integrated urban wastewater and food waste treatment facilities – is huge, and with it, the development of a major economic force that provides renewable energy and food security manages waste, protects water bodies, restores soil health, improves air quality, promotes health and sanitation, and creates mass employment.
The inaugural edition of Bioenergy International’s Digital Biogas Special is a dedicated compilation of articles featuring some of the feedstocks, AD technologies (biomass gasification and power-to-gas (PtG) are excluded in this edition) and biogas plants that have previously appeared in regular issues of Bioenergy International in recent years. The choice is subjective and based on what has captured the imagination of the editor in terms of good practice, novelty and potential.