Over recent years, there have been many efforts put to drive the renewables development and implementation. We hear many news about geothermal, solar power, wind and biomass plant development. Many policies have been enacted to smooth the transition towards more using of renewables. Multilateral development banks (MDBs) also offer their knowledge and expertise to the government contributing to this cause. Oftentimes, these renewables require particular criteria to be be satisfied, such as spacious area, huge investment, high demand, acceptability and many others. In the meantime, many researches are being conducted to find new and innovative technologies and to improve the efficiency of the existing renewable technologies.
Yet, there is one interesting idea to produce electricity from plant. Simply put, the idea involves plants and microorganisms and therefore called as plant-microbial fuel cell (PMFC). One design of PMFC has been patented by Dutch researchers from Wageningen University in 2007. Then, the researchers made a start-up called “Plant-e” to further develop the prototype and try to commercialize the idea.
This article will present the idea behind PMFC, strengths and weaknesses, and its potential application in Indonesia. Examples of PMFC application will be taken from Plant-e, one of the startups in the Netherlands that has commercialized the technology.
How Do Plants Generate Electricity?
The principle for generating electricity from plants is similar to the common fuel cell. There are two electrodes: anode and cathode, as well as electrolytes in the common fuel cell. The resulting electricity comes from the fuel (often hydrogen) through a reduction-oxidation (redox) reaction. In the PMFC, the fuel is the organic waste excreted by the plants. The microorganisms around the plant’s roots, also referred to as electricigens, would oxidize the organic waste to produce carbon dioxide and release electron (e–) and proton (H+). The electron would go to anode which then flow through external electric circuit to cathode. This process of electron flow generates electricity. The proton will travel through a membrane to cathode, which then combines with oxygen (O2) and electron to produce water. Similar as fuel cell, redox reaction takes place as well. Meanwhile, in the cathode, the oxygen is reduce to produce water. The Figure 1 illustrates the PMFC mechanism, while the following equations show the redox reaction (assuming that acetate is oxidized by microorganism).
Figure 1. Schematic overview of PMFC.
How Big are the Potentials?
This idea of generating electricity from plant seems unrealistic at the moment. There are still challenges on how to generate the electricity cost-effectively this way. However, if further researches are done to improve the technology, it is possible to implement it in the future. In fact, it has been used in some places in the Netherlands. For example, at the Wageningen University and NIOO where it used to light LED. Given the fact that it has been running means it is also possible to do the same for the other places. Even though the technologies could only light up the house and for small-scale usage, it may still bring significant impacts to some people where the electricity is scarce.
Figure 2. Plant-e tubular system at the Wageningen University to light up LED
According to Nanda (2015) from Plant-e, the PMFC from Plant-e can generate about one watt per square metre. With an optimist scenario, the Plant-e product can be enhanced to produce three watt per square metre. In some un-electrified villages in Indonesia, where some people rely on candles and kerosene lamps for lighting, this technology can bring meaningful impacts. If it is finally implemented, it can deliver economic impacts so the people can save their lighting cost.
It necessitates more deeper and comprehensive researches to estimate the precise potentials. But based on the PMFC idea itself, it has high potential, at least in terms of opportunity for application. As known, in general, Indonesia unelectrified areas are in the rural areas where there are many plants. As long as there are suitable plants, the technology can be applied, assuming the economic and policy factors are taken care of.
What are the Pros and Cons?
The idea of PMFC has been studied for more than 50 years. Up to this day, despite the many studies done, there is still a lot of rooms for improvements. The PMFC application in the real-life situation still have many drawbacks that need to be overcome.
Figure 3. Plant-e tubular system at the NIOO, Wageningen.
First, the electricity generated using PMFC is not able to compete in terms of price, compared to its renewables peers. Second, there is still the issue of scaling-up the PMFC model if it is to be used in a large scale. The PMFC It requires a lot of space to produce the same amount of electricity compare to the other renewables. Third, in terms of financial aspect, it requires a huge initial investment which may be the barrier for some investors to invest in this system. Last, it may not be important as the other aspects, but the esthetic aspect may become a consideration for some people. Should the PMFC model implemented in a big scale, it may disturb the scenery of some places with some of the equipments among the plants.
On the contrary, the PMFC also has many strength points. First, it is suitable in the off-grid areas where the electricity access still does not exist. As long as the areas has plants, it is possible to generate electricity, at least, to light up the streets. Second, to make the system runs, it does not require a vast area as much as its peers, such as geothermal or wind. As what has been demonstrated by the products of Plant-e, it can work in the roof or other. Third, it is an environmental-friendly technology that does not pollute the environment and does not disturb the plant’s growth.
Is it Applicable in Indonesia?
Indonesia is an archipelagic country with thousands of islands. Moreover, there are still many rural areas that unelectrified. Some of these areas usually are occupied with farmers who work in the agricultural sector. Therefore, there are many plants that are potential to be utilized for the PMFC.
Figure 4. Indonesia rural areas with many plants. Source: picswall.com
Taking the product example of Plant-e, it can be seen that PMFC technology requires plants in a relatively wet area, such as rice paddies and mangrove.; and hence, it is suitable with some of Indonesia’s unelectrified areas. As far as this concerns, the PMFC can be applied.
However, before any conclusion is derived, there are several perspectives that need to be considered. In particular, in terms of technology applicability in a new areas, there will be technology, socio-economic and policy factors associated with it. Apart from that, the PMFC applicability can be analysed from several angles: theory vs implementation and short-term vs long-term.
Theoretically, it has been proven that the PMFC model can work as shown by the Plant-e. It is possible to generate electricity using PMFC but the question remains is to scale-up this model. To supply electricity to the households using PMFC would require a vast amount of areas, using the current technology. However, it does not necessarily mean that it could not be scaled-up. There is still a lot of homeworks to develop the technology to improve its efficiency and make it more cost-effective. In the Indonesia’s context, where there are still many remote and off-grid areas, such an idea brings a fresh air. Even though there is already an option such as solar panel, an addition of other alternatives does not hurt.
On the implementation side, for a large-scale use, the PMFC is still far from reality. If it is only used for street lighting, it might be possible. At this moment, the technology still requires many improvement. Furthermore, there are economical and political aspects that need to be considered. Economic-wise, the technology is not competitive in terms of price, and therefore it is unlikely to attract investment. Unless there are special grants and incentives provided, the utilization of PMFC may not be preferable compared to the other options. Meanwhile, policy-wise, the existing policies have not sufficiently regulated the PMFC implementation as the PMFC itself would be a new and radical technology. Hence, there are some changes necessary to enable the PMFC implementation in the off-grid areas. For example, to attract investment for PMFC, laws and regulations related to incentives for this technology need to be enacted. Other aspects such as PMFC developers and electricity price also need to be regulated. In summary, PMFC is not ready to be implemented yet right now even though it works theoretically.
From the time perspective, as explained previously, it is not applicable in the short-term. Even at this moment, government still struggles to create policies that would attract investment for other renewables. However, in the long-term, the PMFC can be applied in Indonesia. The PMFC and other renewables such as solar energy could complement each other to provide electricity for people without electricity access.
Many rural areas in Indonesia still lack access to electricity. Over the past decade, Indonesia has strived to increase the renewables in the national energy mix. Not only that, program such as solar panel utilization has been promoted to provide electricity in the remote and off-grid areas. There are many technologies being developed and implemented to meet the renewable energy target.
Currently, one of the extensively studied technology is PMFC, which is to utilize plants for the purpose of electricity generation. The electricity generation using plants or PMFC technology has been studied for many decades. The technology is proven to work, for example, in the Netherlands. It can be used to generate electricity for street light or phone charging station. The technology is not perfect yet and there are still many aspects that need to be enhanced, such as efficiency and cost-effectiveness.
Taking the Indonesia’s remote and off-grid areas characteristics into consideration, it is possible to implement the PMFC technology. The PMFC offers many benefits should it be implemented, especially in realizing the Indonesia’s goal to provide electricity and to increase renewable energy mix. However, there are still many technology, economic and policy challenges that are associated with the PMFC. If these challenges can be tackled sufficiently, then it would be feasible to apply the PMFC for off-grid areas electrification. This, however, would still need a long time to be realized. In the meantime, more researches need to be conducted to improve the technology. In addition, many studies are also needed to calculate and estimate the precise potential impacts as well as to formulate and design the appropriate policy framework for the PMFC application in Indonesia.
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*This opinion piece is the author(s) own and does not necessarily represent opinions of the Purnomo Yusgiantoro Center (PYC)