15 June 2020

Biogas has many positive sides – but it’s not best at everything. A source of energy should be analysed from several perspectives – energy, environment and economy – and compared with the alternatives. It is also important to determine which factors of the comparison are important. These are some of the conclusions in a thesis recently presented at LiU.

Biogas plant in Lidköping.
Gasums biogas plant in Lidköping. In a new thesis biogas is evaluated and compared to other alternatives. Photo credit: Gasum.

Many advantages

It has a low impact on the climate, is renewable and an important part of the transition to a sustainable energy system. It produces less waste, and can provide biofertiliser to be used in agriculture. And it’s part of a local circulation. The advantages of biogas are indeed many and uncontroversial.

Emma Lindkvist.PhD! Emma Lindkvist the day after her disputation. Now she can look forward to two months vacation. After the summer she'll work at LiU. Photo credit: Mikael Sönne

But the use of biogas is also complex and difficult to analyse. Several substrates (such as manure, food waste and abattoir waste) are used in its production, and the gas can be used either as vehicle fuel or to produce electricity and heat. The production process often involves several technical solutions and its manufacture is often integrated with other activities. Furthermore, the by-products can be managed and used in several ways.

Another fact that must be considered is which factors are to be evaluated when biogas is compared with other sources of energy. And the level at which the comparison is to be made: is it between individual factories or larger production systems?

Important with knowledge

In her thesis, System studies of biogas production: comparisons and performance, Emma Lindkvist, doctoral student at the Division of Energy Systems, examines these questions. She describes system analyses of biogas production systems and investigates how such systems can be compared.

A biogas production system has several aspects: raw materials, production processes, and how the gas produced is used.

“Analyses and comparisons are important to increase our understanding of biogas systems and the influence they have on the world around us. Further, greater knowledge makes it easier to justify an increased use of biogas solutions”, says Emma Lindkvist.

The thesis presents studies of biogas production at several system levels – everything from individual biogas facilities to large systems with several producers and food manufacturing companies that deliver raw materials. Emma Lindkvist not only suggests a common classification system for European biogas facilities to make comparison easier: she also develops a method to analyse the energy need at different production plants. In both cases, her work makes comparisons easier.

Mostly best

The thesis also examines how organic waste can be managed in different ways, taking the environment, energy and economy into consideration. It looked at five Swedish regions and compared what happens today with a future hypothetical production of biogas.

The result: The production of biogas would be better from an environmental point of view (acidification, impact on the climate and eutrophication) than the current system in all five regions. From an economic perspective, biogas comes first four times out of five. When it comes to energy, biogas is better in two regions, while it is better to continue using the existing electricity production system in three.

Emma Lindkvist.Emma Lindkvist.

Thus, biogas wins in 11 of 15 comparisons. So – how “good” is biogas? The answer, naturally, is: “It depends”.

“Indeed. It depends on the current conditions, and what biogas is to replace. There is, of course, a huge difference if the current system is electricity from coal-fired power stations or from wind power. And it must be remembered that considerable energy is consumed when upgrading biogas to vehicle fuel.”

And it also depends on values – what we consider to be positive and important, doesn’t it?

“Yes, that plays a role, of course. As a researcher, I try to apply value judgements as little as possible. But a company may consider profitability to be most important, while politicians, for example, give priority to other aspects.”

In general, Emma Lindkvist believes that the results presented in the thesis strengthen the perception of biogas as an extremely eco-friendly and economically advantageous alternative energy source. The advantages of biogas are often large and easy-to-see, and there are no serious disadvantages. It is, at the same time, important that biogas is used in a manner that gives most benefit.

Translated by George Farrants

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