Part One: Green Fuel.. Literally!
These single-celled celled photosynthetic organisms need no encouragement to grow in any aquatic environment (think of the blue-green algae that regularly invade Tatton Mere). They use the sun’s energy to convert carbon dioxide into lipids – oily substances that can be readily extracted and processed into high grade fuel.
Most bio-diesel currently being produced comes from high oil containing crops such as soybean in the US, jatropha in India or rapeseed in the UK. These crops take up valuable food-producing land which is a massive drawback. This has also prompted big concerns over other plant derived biofuels such as bio-ethanol which is made from sugar cane or corn in areas of the world where children still go hungry. Algae, on the other hand, can be cultivated in massive ponds constructed in deserts or other wastelands.
They can also grow much faster than plants, doubling their biomass in a few hours in the right conditions. Finally, algal ponds require far less land area. Boeing estimates that less than 1% of the land area of the Sahara Desert could provide the world’s entire aviation fuel needs.
Another big advantage of algal derived fuel is that it is sustainable and can be made to be better than carbon neutral. Algae are hungry for carbon dioxide which dramatically increases their growth. Bio-diesel ponds could be therefore be sited next to conventional power stations to absorb the CO2 rich flues gases that they pump out.
There are still significant technical problems to overcome but funding from sources such as the UK’s Carbon Trust is attracting the best scientific minds to optimize yields and design the most efficient mass-culture methods.
We still need to find out why algae produce oils in the first place. It seems to be related to their response to stressful conditions such as high salinity or nutrient starvation. Once they understand this process, scientists will be able to start controlling it to increase oil production.
There are over 30,000 different strains of algae which are being screened to find the best producers. Dr Jim Gilmour from Sheffield University’s prestigious Department of Molecular Technology and Biotechnology is particularly interested in a strain of algae called Dunaliella salina. “This type of algae is an example of an extremophile since it can tolerate salt concentrations up to ten times that found in seawater” explains Gilmour. “This makes it an excellent candidate for bio-diesel production since it can be grown in concentrated seawater ponds in arid areas. Even better, there is far less chance of pond contamination by competing microbes since very few can live in such saline conditions”.
Another intense focus of interest is how to extract the valuable oils from within the algal cells once it has been synthesized there. The crudest option is to break up the cells and extract the oils using organic solvents. A more subtle approach uses high power ultrasound waves to gently coax the lipids from the cells. “In this so-called ‘Algal Milking’ approach we keep the cells intact” says Jeremy Hawkes, a researcher in the Department of Chemical Engineering and Analytical Science at Manchester University. “It’s far more efficient to have a colony of cells continuously secreting the oil than destroying them and growing new cells from scratch”
How long before we’re pumping truly green fuel into our cars? It’s a possibility 20 years from now given the uncertainties over the reserves of fossil fuels and the increasing momentum for sustainability. Green slime might save the planet one day.