Growing your own power plant on the roof in the future

We need more clean energy in our homes. There is a trend to micro-generation that can be used to ensure that the houses of the future are carbon and even energy neutral. The problem with two of the main methods solar and wind is that these only work when – the sun shines or the wind blows.

However, reading an article by Caroline Williams in New Scientist, I was alerted to the fact that growing plants can themselves be used to generate electricity. Marjolein Helder and David Strik in the Netherlands have founded the company Plant-e, aiming to develop commercially useful plant based energy generation systems.

The principle is remarkably simple. Plants take the carbon dioxide in the atmosphere and fix it into sugars and carbohydrates. These are in part secreted by the roots where they are digested by bacteria. In the process of digestion, the bacteria generate hydrogen ions and electrons (see their figure here http://www.plant-e.com/technology.html). In a wet soil, these ions can migrate.

Add two graphite electrodes and you can draw a small current of electricity. Importantly, the current is generated day and night, without detriment to the growing plants.

Currently (excuse the unintended pun) research is underway to improve the power gain. There is an EU collaboration between different research groups and companies aiming to achieve this called PlantPower. Plant-bacteria power generation is likely to be  five times more efficient than using the same area to produce biofuel.

Visiting Ecobuild last week, I saw that there is an increasing interest in using green roofs on buildings, both to retain runoff water and also act as habitats. It now looks as if in the future green roofs could also be used for power generation.