Part 2. Bottled biogas: why isn’t the genie in the bottle yet?

By Matt Leach, MECS Gamos Associate, and Professor at the University of Surrey

[This is a second (and final) blog relating to the biogas potential working paper. Access the first blog here].

A recent MECS working paper asks whether biogas in small cylinders has a role to play in modern energy for cooking in Africa .

In the blog Bottled biogas: why isn’t the genie in the bottle yet? Part 1, I wrote about biogas and bottling and concluded that while there has been some experimentation, the evidence base about this potentially exciting clean cooking option is sorely limited.  In this blog I try to answer the question – so why aren’t African agri-businesses across the continent benefiting from a new market for their residues and African householders carrying clean-burning and low carbon bio-methane cylinders home from the market, in an economy-health-environment win-win-win?

This was the question we posed at the start of 2019 for a scoping study on bottled biogas for Africa, undertaken by researchers at the University of Surrey, the Kwame Nkrumah University of Science and Technology in Ghana, the Uganda Cleaner Production Centre and Engas UK, an innovator in gas cleanup and compression. The study was primarily funded by Research England, but MECS provided matched funding, allowing us to engage with a much wider group of international specialists.

What are the barriers, and how do we overcome them? Literature review established the state of the art in technology; stakeholder interviews and field visits with agri-business and waste companies in Ghana and Uganda explored the potential biogas feedstocks, markets and policy issues; simple techno-economic modelling tested the business model and finally a two day conference was held to bring public and private sector players from Africa together with biomass specialists from Europe and with leading Indian researchers.

The science of anaerobic digestion is well known, and it is commercial in developing as well as industrialised regions, but most efforts go into sophisticated technologies, with high capital costs and onerous operational management, best suited to relatively large commercial scales. But the study demonstrated the potential viability of small-scale bio-methane plants, driven by lower capital cost of a simpler gas upgrader and compressor, with clever systems integration.

Engas UK’s bio-methane plant.

The nature and continuous availability of the feedstock is key, on the ‘what goes in must come out’ principle, such that feedstock quality affects clean-up complexity. Promising options were found to include the treatment of waste from livestock facilities in Ghana and the treatment of effluent waste from alcohol production facilities in Uganda. The relatively simple financial analysis looked at three scales, from a micro facility refilling just 4  bottles a day to one an order of magnitude larger. The focus was on the viability of an investment that could produce bottled bio-methane to compete on cost with cooking using LPG. For Ghana, where LPG refill prices are mandated at $1.08/kg, only the largest system achieved a payback period of less than 4 years, and the smallest system wouldn’t payback at all. But in Uganda, where the LPG refill price is typically $2.6/kg, all three system sizes achieve payback times below 4 years.

The financial analysis was admittedly very simple, and for example took no account of investment financing costs; however it focused only on income streams from selling gas for cooking. But long experience with waste-to-energy facilities in Europe has shown that it is not sensible or necessary to try and make a business from the value of energy alone: it is the avoided cost of disposing of waste, as it becomes feedstock instead, that drives the economics. So the business case for bio-methane bottling requires a systems view across the supply chain of the agri- or waste- business, valuing waste disposal as well as energy benefits, and taking on risks of feedstock as well as of the fuel market. This is the modern challenge of producing a Circular Economy, towards which policy-makers the world over aspire, but struggle.

System view; adapted from World Biogas Association (2014).

There is a second potential stumbling block. High pressure steel cylinders filled with bio-methane would have a similar filled-weight to same-sized LPG cylinders, but the energy content would be less than half. You could squeeze more gas into higher-pressure composite material bottles, at higher capital cost, and this is being pursued actively for sustainable transport. Alternatively, the household cook would need to make more frequent trips to refill: the study didn’t set out to look at this user-experience aspect at all, but it is clearly a central driver to uptake.

The prize of a storable cooking fuel, coming from sustainable sources, is large, and the study has shown that bio-methane is a feasible route. Hopefully the newly assembled evidence base in the working paper will help convince the sceptics that there is something worth exploring. But the path is not a straight one, and it isn’t clear yet if it is a scenic route, and hence not many are yet embarking on the journey. The next steps need to be pre-commercial demonstration and then commercial scale piloting, in the African context, to explore real-world costs and the user experience, to smooth the path and signpost it, before any uptake at scale could be expected.