The Nonsense Of Biofuels: Thoughts From A Nobel Prize Winner
Prof. Hartmut Michel calls for resources used in biofuel production to be used instead to harvest solar energy with photovoltaic cells.
AsianScientist (May 2, 2013) - Professor Hartmut Michel is a man on a mission. Fed up with the hype over biofuels, the Nobel Prize winner is out to convince us of the futility of biofuel production and that harvesting solar energy with photovoltaic cells is a far better alternative.
Often described as carbon dioxide-neutral and a weapon against global warming, biofuels have been touted as a solution to the world’s dependence on fossil fuels by making countries less dependent on imported petrol and natural gas. According to the International Institute for Sustainable Development, governments around the world have thrown their support behind the development of biofuels and poured more than US$20 billion into subsidies for biofuel production and consumption.
However, the zeal with which governments have latched onto the promise of biofuels has ignited a "food versus fuel" debate over the value of using arable farmland or food crops for biofuel production. Commodities such as maize, sugar cane, and vegetable oil are not only common food sources but can also be used to make biofuels. Government policies, for example in the US, the EU, and Brazil, have diverted these crops toward this purpose, to the impoverishment of the global food supply.
Prof. Michel, who was awarded the Nobel Prize in Chemistry in 1988 for discovering the 3D structure of the photosynthetic reaction center found in certain bacterial membranes, is the director of the Max Planck Institute for Biophysics in Frankfurt, Germany. He had previously penned his views on biofuels in an editorial and gave a seminar to share his thoughts while in Singapore last week as the Chief Judge of the Agency for Science, Technology and Research (A*STAR) Talent Search competition.
The limitations of photosynthesis
As a global leading expert on membrane protein chemistry, Prof. Michel has a deep understanding of the efficiencies of photosynthesis. Looking first at how plants convert energy from sunlight to a usable form known as NADPH, he outlines how the photosynthetic pigments of plants only absorb up to 47 percent of sunlight, while green light, ultraviolet and infrared light are not used. Importantly, calculations reveal that only about 12 percent of sunlight energy is converted and stored.
Turning to yields of biofuels per hectare of land, Prof. Michel explains that biogas produced in Germany yields only 0.3 percent of sunlight energy, while other biofuels such as biodiesel and bioethanol yield even less. In addition, more than 50 percent of this yield had to be invested in the first place in things like fertilizers, ploughing, and transport to obtain the biomass for conversion into biofuel, he says. In Central Europe, where the value of arable land is about 150 W per square meter, the maize grown for biogas yields a puny 0.2 W of electric energy. This works out to a production efficiency of only 0.13 percent, he says.
"The production and use of biofuels therefore is not CO2-neutral," says Prof. Michel, and growing crops for biofuel "is a highly inefficient usage of land."
"It would be much better to grow poplars on the land used for biofuel production and to convert the biomass to coal by hydrothermal carbonization," he says. Such a process involves heating the biomass in water to 160 degrees Celsius and has been reported to capture 100 percent of the available carbon. Doing so would save up to a whopping nine times more carbon dioxide per square meter compared to biofuels.
"Direct usage of biomass for heating or electricity conversion in power plants is more efficient," says Prof. Michel.
To increase yields, Prof. Michel suggests that scientists could study how to improve light absorption of plants by modifying the pigments in the photosynthetic machinery. Photosynthesis is in fact most efficient at low light intensities and becomes saturated at one-fifth of full sunlight, he explains, and RuBisCO, an enzyme involved in fixing carbon dioxide into an energy-storage form, could be an attractive target for scientists to improve by engineering. An indication that this is an achievable goal is that a more efficient form of RuBisCO already exists in red algae, he says.
Photovoltaics is the way forward
However, Prof. Michel believes there is a better alternative to photosynthesis: photovoltaic cells for production of electricity. Commercially available photovoltaic cells have conversion efficiencies of more than 15 percent, he says, which is 150 times better than energy storage in biofuels. Importantly, he adds that this energy can be stored in batteries used to power vehicles.
Outlining his daring vision, Prof. Michel would like to see three to four large photovoltaic fields built in deserts across the globe. One would be in North Africa, in the dunes of the Sahara or the Kalahari desert; another in the Taklamakan desert in China or in the Gobi desert that straddles the border between China and Mongolia; one in Australia; and the last in Mexico. Connected by a network of superconducting cables, he says that these super energy farms "would be sufficient to supply all electric power which mankind needs."
Such an ambitious plan is not without precedent. Prof. Michel raised the example of the Desertec Foundation established in 2009 that has proposed transporting energy from the Middle East and North Africa (MENA) region to Central Europe via high voltage direct current cables. The Foundation cites studies performed by the German Aerospace Center that demonstrate the suitability of the desert sun to meet rising energy demands in the MENA region. Scientists believe that the region would not only be able to fulfill its requirements with renewable energy but also generate excess energy for export, thus creating an industry worth more than €60 billion annually.
Prof. Michel is a big believer in electric cars and these cars must run on electricity directly derived from sunlight. He explains that combustion engines "use only 20 percent of fuel energy for propulsion," while electric cars use 80 percent of the sunlight-derived energy stored in batteries: an incredible 400 times more efficient than cars with biofuel/combustion engines. But before this can happen, Prof. Michel calls on engineers to develop more powerful batteries than the lithium ion batteries we have today. He points toward emerging technologies such as "novel tin-lithium-sulphur [batteries that] can store ten times more energy."
Perhaps these are all lofty dreams of a Utopian world. But for a man who was awarded a Nobel prize at just 40 years of age, Prof. Michel likes to dream big.
"The future of our individual transport has to be electric!" he concludes.
Copyright: Asian Scientist Magazine.
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