R&D company Plant-e uses plants to generate electricity. ETE played a key role in designing and improving the efficiency of this so-called Plant Microbial Fuel Cell. Now Plant-e is further developing the technology to boost yield and reduce costs.
A red and a black electrical wire stick from the soil of a small plant pot. Pim de Jager, researcher at Plant-e, connects the two and a small LED lights up. Electricity from plants, a green dream that has become reality! ‘Bacteria and plants live in symbiosys’, de Jager explains the principle. ‘The plant uses solar energy to synthesize organic compounds for growth. Part of these substances are released by the root system into the soil, and utilized as fuel by bacteria.
‘Metoprolol has just one stable phenyl ring, that can obviously be degraded by micro-organisms present’, the scientist concludes. ‘The deployment of bacteria to enhance micro-pollutant degradation should be tested and whenever effective implemented in waste water treatment systems.’ In this process electrons are formed, that can be harvested by an electrode to generate electricity.’
The principle of micro-organisms generating electricity was first discovered in wastewater treatment systems. An important part of this water cleaning process includes the bacterial removal of organic compounds. Scientists found out that these microorganisms converted organic contaminants into biomass, while producing CO2, hydrogen ions and electrons. By placing a positive (cathode) and negative (anode) electrode into wastewater, electrons were formed at the anode and could be harvested. Closing the circuit resulted in an electrical current. This principle was subsequently applied in the microbial fuel cell (MFC). Soon, scientists discovered that plants and their symbiotic soil bacteria could replace waste water (fig. 6). As soon as the proof of principle was demonstra-ted, in 2009, spin-off company Plant-e was founded.
For CEO and founder Marjolein Helder, the establishment of Plant-e was a gradual process. During her Ph.D. she built the company step by step. Grants and personal loans generated hard cash. ‘There is now about one million euros in Plant-e, including 250,000 euros in personal loans and many hours of unpaid work’, Helder says. I don’t consider this a risk, because I strongly believe in the product. I cannot imagine it won’t work in the end!’ Plant-e built the first working system where plant power was generated in 2011, on top of the roof of the Netherlands Institute of Ecology (NIOO-KNAW) in Wageningen. The system was used to perform experiments and to collect data.
Many improvements were made and even though some obstacles still need to be taken, Plant-e decided to commercialize the product at an early stage. By the end of 2014, the first commercial systems were launched. ‘We have developed the basic technology into a system that can be applied in real life’, says Helder. ‘Our current commercial system consists of several modules, series of plant trays of about 50x50 centimetres, generating 5 Volts of electrical voltage.’ According to the World Economic Forum, Plant-e has developed into one of the most innovative firms in the world.
According to Helder, it is too early to use the system as an alternative to generate electricity. Helder: ‘Our invention is more like an integrated product with plants, that delivers electricity and has a great appearance! It is meant for customers who want to lead the way and appreciate a beautiful green gadget.’ An area of 100 square meters costs about 60,000 euros and provides enough electricity to recharge a mobile phone or to illuminate several LED lights. Local and central governments appreciate the technology and its potential and purchase the system, supporting research and development. For example, in the building of Interpolis in Tilburg, plants supply energy to a mobile phone charging unit, while a plant-powered wifi-hotspot was built on a schoolyard in Zeist.
Over the years, revenues for Plant-e have increased gradually, reaching about 700.000 euro in 2016, the first year that the company reached break even. But there is still a long way to go before the system is efficient enough to compete with other energy sources. Despite obvious challenges, Plant-e expects that further research and development will result in a dramatic increase in efficiency.
But to increase efficiency, a better understanding of how the system works is needed. ‘Our research now focuses on the basics of the system’, say Pim de Jager. ‘For example, we need to know more about species of bacteria that contribute and what compounds, the fuel, they prefer to generate electricity. Increasing these substrate concentrations, for example by supplying the right fertilizers to the plant, might result in a better efficiency.’
Clean energy supplier
Not only bacteria, but also the plant species effects the amount of electricity formed, since the amount and type substrates excreted by the roots differs between species. Grasses do particularly well, as long as they grow in a water-saturated soil, with little oxygen. For this reason, Plant-e is currently developing a tubular system that can be submerged in moist nature areas like wetlands, flood plains or rice paddies. The system works in the lab and is now being tested at two locations in the Province of Brabant and Zuid-Holland. If these tests succeed, nature as a clean energy supplier is within reach.