Tiny, microscopic algae may seem like an unlikely replacement for today’s fossil fuels, but recent advances in technology are turning them into a candidate of increasing potential.
In order to offer a viable alternative to oil or natural gas, the microalgae have to be produced sustainably, and fuels derived from them have to be compatible with today’s distribution grid, while also being able to power a wide range of applications, from power plants to cars, at an affordable cost.
Biomass abounds on Earth, as forests, fields, sewage and seaweed. But only a small fraction, mostly human or agricultural waste, can be harvested without posing environmental risks.
If we want bio-energy to be a meaningful slice of tomorrow’s energy pie, we need to actively grow more of it.
But why choose microalgae over corn, soy, or the other crops that are already being grown around the world to produce bio-diesel or bio-ethanol?
Because there is more to sustainability than a low carbon footprint. Fuel crops have to be grown somewhere, and if they’re grown on land currently used for food crops, that means less food for us.
Microalgae are among the fastest-growing plants on the planet. Thriving on a diet of sunlight, water and carbon dioxide, they can be grown in aqueous suspension on inexpensive, unfertile land.
And although a lot of effort has already been spent to produce bio-diesel and bio-ethanol from microalgae, the financial and energy costs of growing and processing them has kept this approach from becoming competitive.
Over the past years, we have been working on the SunCHem process, an alternative pathway to convert wet biomass such as microalgae into methane, a biogas.
Methane is relatively easy to distribute via the world’s existing and growing network of gas pipelines. It can be used to run power plants, heat buildings and fuel cars using technology that is already available today.
In the SunCHem process, microalgae are grown, concentrated, and then gasified, converting them into methane. Byproducts such as carbon dioxide are fed back into the system to grow the microalgae, while salts or other inorganic compounds can be extracted and reused or recycled.
What makes this process so efficient is that the organic fraction of the biomass is converted into methane by exploiting a strange quirk of water. When heated past its boiling point, but pressurised to keep from evaporating, water becomes capable of completely dissolving the organic compounds contained in the biomass.
SunCHem has been shown to work in the lab, and our calculations make us optimistic that we will be able to make it financially affordable and environmentally sustainable in the long run.
There are still challenges. We would like the methane-producing catalyst to last longer, for example.
The next step is to test the process outside the lab. To do so, we are currently setting up a bio-methane production plant in a shipping container that will let us run pilot studies using different types of algae to fine-tune our process. And with additional funding, we hope to run a larger-scale pilot study.
Creative business models, similar to those used in today’s petrochemical industry, could help further bring down prices. A new “bio”-chemical industry could, for example, exploit high-value chemical compounds that can be extracted from microalgae for pharmaceuticals, cosmetics, foods, or fodder, producing bio-methane as a side-product. And the algae could also be used to treat the actual water they grow in.
Microalgae may never produce as much power per square metre as solar panels, but if grown where land is cheap and sunlight abundant – places such as industrial zones or near wastewater treatment plants along the UAE’s west coast, for example – they could, in the near future, provide a viable alternative to today’s fossil fuel resources, which are not just used for fuels production but also essential for the fine chemical industry.
Christian Ludwig is a professor in solid waste treatment at the Paul Scherrer Institute in Villigen and the Ecole Polytechnique Fédérale de Lausanne in Switzerland.