I often get asked, “why use biomass for energy when it is more expensive than other renewables?”
The answer is complex but, in its essence, simple: because it is cheaper.
How can something be both more expensive and cheaper at the same time? Well, we must consider both the amount of energy and time of delivery when we talk about electricity.
With biomass you can decide when to produce electricity, whereas with solar and wind one needs to add storage to the equation to have the luxury of power “on demand”. This, however, means that storage losses and capital cost must be considered.
If the cost of solar in the UK is £45/MWh1, adding batteries to smooth out demand over the day would append an extra £54/MWh2, resulting in a total cost of £99/MWh, a level comparable to that of biomass. Over the year, this number would amount to a staggering £4,000/MWh3 when you include battery costs.
Don’t get me wrong, solar, like biomass, has inherent benefits. Solar technology is a crucial element in the range of renewable energies available today. Just like wind, it is an effective tool to reduce our dependence on fossil fuels. My point is that there are obstacles in directly comparing two different technologies.
The cheapest way of decarbonising power and heat grids is through a variety of variable renewable energy technologies like solar and wind as well as firm dispatchable, always-on resources like biomass. That is why we should use solar and wind in conjunction with biomass.
Biomass is cheap – Hydrogen can scale
Woody biomass is a great idea when it is produced as a by-product from forests that primarily function to supply timber in all its forms: construction beams, fence poles, railway sleepers, boards, furniture etc. – that otherwise would be made from concrete, steel and plastics, resulting in more carbon emissions.
When used in power stations to replace coal, this renewable energy source provides a fast and low-capital cost option to rid our power and heat systems of fossil fuels. Unfortunately, there is a limit to the amount of biomass that can be produced while ensuring that forests are growing and storing more carbon.
The case for hydrogen is different. There is an endless opportunity to scale this promising new technology, and it has the potential to decarbonise shipping, heavy goods transport and, in conjunction with Bio-energy Carbon Capture and Usage (BECCU), one day perhaps also air travel.
As I see it, the biggest issue with hydrogen in context of power and heat is that it will always be costly and that we are still decades from advancing this technology to a level where it can be deployed at scale.
When renewable energy is turned into hydrogen and back into power, there is a substantial energy loss: an initial 30% is lost in the electrolyser4, a further 40%5 in the process of creating storability and converting it back into hydrogen. Finally, hydrogen needs to be turned back into power, which again leads to a loss of 40% to 60%, depending on the solution. Altogether, only around 20% of the initial energy produced will eventually become power6, often referred to as round-trip efficiency.
To compete with biomass – the only other dispatchable technology in the renewables range – hydrogen would need to be produced from a renewable source that is five times cheaper in energy terms. This could be the case of, say, solar in the Sahara or the Australian outback. The problem is that all the above applies before considering capital expenditure. For example, if you rely on solar power to produce hydrogen you can only expect to run at 25% of maximum capacity on average7 – which makes capital cost four times higher than running it at full load.
There are ways to improve this round-trip efficiency substantially by using reversible fuel cells and heat exchangers. It is also possible to improve the utilisation of hydrogen plants by adding batteries to even out daily solar generation. Together, advances in technology will hopefully bring down all-in costs over time and deliver a scalable solution to replace all fossil fuels in power systems across the world.
Biomass for power and heat (and future feedstock) – hydrogen for transport
Without doubt, solar and wind will become cheaper in the future; so will batteries, fuel cells and the conversion of renewable energy. But we are still a long way from economically replacing biomass in the power and heat sector.
Hydrogen – either pure, as ammonia or other liquid fuel – promises further advantageous milestones ahead that could result in oil and gas being phased out in heavy industry and transport applications. Once it becomes abundant and cheap enough to compete with biomass on a cost basis, forest residues can be diverted to biorefineries to substitute oil and gas as feedstock in various sectors that will be most difficult and costly to decarbonize.
For now, however, this remains a vision of the future. When it becomes reality, we will have come a long way.
Jens Wolf is vice president and general manager of Europe at Enviva, the world’s largest producer of sustainable wood pellets.