Friday, 28 February 2014

Talk : Green Fuel from Seaweed

A recent Cafe Sci Event featured a fascinating talk by Emily Kostas (Faculty of Science, University of Nottingham (Sutton Bonnington Campus)). The talk was entitled "Green Fuel : Environmentally Friendly and from Seaweed" and gave an insight into Emily's research project on converting seaweed into biofuel and other marketable products. This post is based on Emily's talk, with some extra linkage thrown in.

Current UK legislation supports the development of biofuel technologies by mandating that all petrol and diesel sold must have 5% biofuel.

The use of biofuels is not a recent development, indeed, Rudolf Diesel, who invented the engine that bears his name, said in 1912 that “The use of vegetable oils for engine fuels may seem insignificant today, but such oils may become in the course of time as important as the petroleum and coal tar products of the present time.”

Any new biofuel technology has to go through a series of stages before it becomes a commercial proposition. Work typically starts at the lab scale before progressing to a small scale pilot plant and then a demonstration production facility. If the numbers still add up then the process can make the jump to supplying commercial quantities of biofuels.

A shockingly bad picture of Emily during the Q&A session

Different technologies are, unsurprisingly, at different stages along this path.

Ethanol from sugar and starch is certainly a commercial activity, as seen by the use of sugarcane as a feedstock in Brazil .

Biodiesel from Esters, which uses feedstocks such as vegetable oil, is another technology that is in commercial production.

Lignocellulosic ethanol processes aim to produce fuel from the inedible "woody" parts of plants and trees - but breaking down the lignin in these materials is a formidable technical challenge, and these technologies remain in the demonstration plant stage.

Macroalgal processes, using seaweed as a feedstock, are still in the lab stage of development but offer some advantages (as well as some challenges) compared to other technologies.

A map of the current biofuel plants operating in the UK can be found here.

Focussing more closely on seaweed, Emily described how there are three main types of seaweed : Brown, Red and Green, with their differing colours being due to the varying depths (and thus light intensities) that they live at.

Whilst seaweed is famously used as a food source in the far east, in the west it is used more for the production of food supplements and additives, or medical materials such as alginate and agar.

Emily brought along some seaweed
for people to have a look at!

Seaweed has a number of features that make it attractive for ethanol production:
i) A high sugar content (more sugar = more ethanol)
ii) No lignin (the "structural" component of land plants - hard to break down)
iii) No freshwater required
iv) Does not compete with grazing land
v) Grows quickly

But also some features that present a challenge:
i) High water content
ii) Sugar content is variably through the year
iii) Needs to be transported to land

In addition, another challenge is that the yeasts used in current fermentation processes (to convert the sugars to ethanol) do not work on the mix of sugars found in aquatic plants such as seaweed. This is because yeasts have evolved to live with land based plants. So new (possibly GM modified) strains of yeasts are required to ferment the sugars found in seaweeds.

Kelp Forest

Emily also showed a chart that compared the amount of bioethanol that could theoretically be produced from different feedstocks (measured in litres per hectare per year):

Wheat1010 litres
Corn2010 litres
Sugarcane6756 litres
Seaweed23,400litres (!)

While a Carbon Trust Report gives a feel for the proportion of biofuel that might come from macroalgae by estimating the likely amounts of differing biofuels in the year 2050, and calculating their energy equivalence (NB: 1EJ = 10e18Joules!)

Woody/Grassy Crops69EJ
Oily Crops4EJ

Emily also mentioned some of the other seaweed-as-a-fuel projects in Europe:

BioMara - a joint UK- Irish project that "aimed to demonstrate the feasibility and viability of producing third generation biofuels from marine biomass."

SINTEF Norway are investigating the possibility of farming kelp off Norways coasts and a news article comments that "...we already have a major industry based on an annual harvest of around 150,000 tonnes of kelp from which alginates are extracted....Although harvesting removes less than one percent of Norway’s standing seaweed and kelp biomass, we do not recommend taking out more than this amount, as kelp forests are actually important nursery and feeding grounds for a wide range of invertebrates and fish. If we want to expand our kelp-based industry, we will have to cultivate kelp on a large scale"

Indonesian Seaweed Farm

The SuperGen Bioenergy Hub, which aims to "bring together industry, academia and other stakeholders to focus on the research and knowledge challenges associated with increasing the contribution of UK bioenergy to meet strategic environmental targets in a coherent, sustainable and cost-effective manner."

The Seaweed Biorefinery Project aims to convert native seaweeds to chemicals, biofuels and energy.

A lot of useful information can also be found in this Technology Strategy Report and also in this, seemingly even handed, report commissioned by the Scottish Government.

Image Sources
Farm, Forest

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