Using Solar Energy As Transportation Fuel

Photo Synthesis

Photosynthesis is a process used by plants and other autotrophic organisms to convert light energy, normally from the sun, into chemical energy that can be used to fuel the organisms’ activities. Carbohydrates, such as sugars, are synthesized from carbon dioxide and water (hence the name photosynthesis, from the Greek φῶςphōs (gen. φωτός, phōtos), i.e. “light”, and σύνθεσιςsynthesis, i.e. “putting together”) during the process.

(Wikipedia)

To my knowledge there are two ways of directly capturing the sun’s energy: (a) via photvoltaics (solar cells) and (b) via photosynthesis (biomass). In our business we are continuously exposed to some of the debates about alternative energy, transportation fuels, carbon capture, etc.. On these topics, we analyse vast amounts of (sometimes complex or complicated) debates as well as research output and try to understand them from a simple and practical point of view:

What is the socio-economic benefit of the information that is in front of us and how will it change the world that we’ll leave behind for our great-grand-children?

Sunlight

Whilst photvoltaics offer a more efficient conversion of sunlights to energy than plants, the conversion or use of electricity as a transportation ‘fuel’ is unable to compete with sun-energy that is derived from biomass.

Handbook of Bioenergy Economics and Policy By Madhu Khanna, Jèurgen Scheffran, David Zilberman

Handbook of Bioenergy Economics and Policy
By Madhu Khanna, Jèurgen Scheffran, David Zilberman

Although the above table has to be read in the context of biomass yields (see chapter 2), it explains to me why sugar cane and oil palms are currently the leading  crops for liquid biofuels. Of course, there are other factors that influence the choice of feedstock, like productivity, i.e. yield per ha per annum or water usage or the crop’s impact on soil health.

The main driver behind alternative transportation fuels is the reduction of green house gases. The above crops have demonstrated a reduction between 37% (Miscanthus) and 98% (sugar cane), which is good. However, biofuels have also a long list of issues that ‘the man in the street’ is not aware of. They are showcased in this wikipedia entry, but I’m unable to find the two biggest ones on that list.

Is there enough land on earth for a sustainable supply of biofuels?

The Based on the 2010 consumption (see below) the World Biofuels Association (WBA) seems to think so.

In 2010, the global biofuel production from sugarcane, oil palms and some other crops reached 104 billion liters. - World Bioenergy Association

In 2010, the global biofuel production from sugarcane, oil palms and some other crops reached 104 billion liters. – World Bioenergy Association

WBA emphasizes there is enough land available to feed a growing population and for the production of biofuels (see 27 March 2013 Factsheet).

Is there enough water?

One of the key ingredient of photosynthesis is water that is converted into the hydrocarbons that ultimately will become the ingredients of the biofuel.

The researchers of the International Water Management Institutes (IMWI) say “it depends”. It depends on the country, the crop used for biofuels.

A fourfold increase in biofuel crops between 2005 and 2030 raises serious concerns for water supplies. Although the additional irrigation water needed to grow biofuel crops is just a few percent of the global total, the impacts in some countries could be highly signicant, with serious implications for water resources. Rapidly growing economies such as China and India are unlikely to be able to meet future biofuel and food  demands without greatly aggravating water scarcity, unless alternative feedstocks are used.

A fourfold increase in biofuel crops between 2005 and 2030 raises serious concerns for water supplies. Although the additional irrigation water needed to grow biofuel crops is just a few percent of the global total, the impacts in some countries could be highly signicant, with serious implications for water resources. Rapidly growing economies such as China and India are unlikely to be able to meet future biofuel and food demands without greatly aggravating water scarcity, unless alternative feedstocks are used.

For example “Producing one litre of ethanol from sugarcane takes nearly 3,500 liters of precious irrigation water in India, but just 90 liters of irrigation water in Brazil. In China, it takes 2,400 litres of irrigation for maize to yield a liter of ethanol.” Read more about it in their Water Policy Brief N. 30.

My conclusion

It is complex and complicated (for the arguments presented above, there are counter arguments). I personally think that biomass is more valuable than to burn it as transportation fuel, but that will be another debate. In the meantime, I conclude that one has to evaluate the ‘most inconvenient truth’ and that is IMHO the fact that the high energy consumers of this world have to slow down. How?

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