Biofuels: The Cellulose Barrier

In congested, polluted central London they are researching the possibilities of making biofuels from trees. They hope that soon, the poplar will become a reliable, renewable source of biofuel.

Said Matthew Nelson, a biologist from Imperial College London: “The first thing that we have to do when we receive our wooden samples is to grind all the material down to a uniform particle size.”

Said Richard J. Murphy, a reader in Plant Science, Imperial College London: “To produce biofuel out of wood, we first need a wood biomass that will have high yield and also the right qualities. The following step involves applying enzimes into this biomass in order to release the sugars that are held inside the wooden biomasses that you see here. The next step is the fermentation of these sugars into ethanol. And the final stage is to concentrate this alcohol, and then it can be used as a fuel.”

It all starts in a series of greenhouses in Nancy, in north-east France where different varieties of poplars are being grown. Wide-spread, fast-growing, and so undemanding that they can grow on non-agricultural land, poplars have been good candidates for biofuel production for years.

Francis Martin, the co-ordinator of the EU Energypoplar Research Project said: “The poplar has an amazing capacity for capturing solar energy. We can see that very well in these leaves which are absorbing solar energy and transforming it into wood and biomass.”

But scientists aren’t just looking for any old tree. They are looking for a “super-poplar”.

Said Francis Martin: “We want to select a poplar which will grow very fast, produce lots of wood, and will simultaneously be efficient at using minerals, and which will have the minimum impact on the environment.”

So they are researching natural ways of improving growth. For example, they have added various fughi to the roots of some samples.

Said Annegret Kohler, a molecular biologist at INRA-Nancy: “After 1, 5 or 2 months, we check whether the funghi has interacted with the plant roots, if it has formed a symbosis with them. Often we can already see with the naked eye that the roots look swollen. That is often a sign that interaction has taken place. We can confirm it under the microscope.”

Molecular analyses have confirmed that certain funghi help some trees to grow faster and more robustly.

Said Valerie Legue, a cell biologist at INRA-Nancy: “This type of inter-reaction means the plant can get more nutrition which means bigger better growth. It’s a big discovery for us, because it’s a common symbiosis in natural ecosystems, whether they are in forests or cultivated plantations.”

Matthew Nelson, a biologist at Imperial College London said: “We have put the wood through a grinder, and then we sieve to a certain particule size, we bag it up and then the wood is ready to extract sugars…”

Back in London, the quest to extract sugars from poplar wood goes on.

Richard Murphy: “What we are trying to do is to find the optimum cell wall structure in the poplar. A cell structure that makes it both a resilient plant that will grow well and yield a lot of biomass, but that will also make a lot easier to process the next quite difficult step, that is to extract the sugars contained in the cellulose.”

Identifying sugar-laden poplars is one of the aims of this giant plantation in Orléans, central France. Around 2,700 different poplars, all from successive controlled crossings, grow here. Researchers want to identify the most resilient and productive trees – in open air conditions.

Said Catherine Bastien, a geneticist, INRA-Orleons: “We are trying to collect trees which start growing relatively early in the season, when conditions are favourable. Then we’ll be trying to find a tree that grows several shoots at once after pruning. We’ll be looking for shoots which develop the maximum foliage. We will also be looking for species which resist the diseases which can attack them throughout the year.”

Selecting a resilient poplar that also produces lots of cellulose requires patient research. And a few imaginative tricks.

Gilles Pilate, a molecular physiologist, at INRA-Orleans said: “These trees are leaning over for a good reason. We are using them to study “reaction wood”. “Reaction wood” is a specific growth which occurs all through the life of a tree and which allows it to resist wind and being pushed over. It means a tree can make its trunk and branches go back to the right position.”

Molecular analyses confirm that this “reaction wood” is richer in cellulose – and thus in sugars – than “normal wood”.

Gilles Pilate: “We can colour the reaction wood, this reaction wood which we find here. And this colouration reveals the cellulose, which shows up blue. So straight away we see the part of the wood – the reaction wood – which is rich in cellulose and thus in sugars.”

Matthew Nelson: “We are going to take our grounded poplar material over to the biochemistry lab. At which point we will expose it to enzymes to see how much glucose, how many sugars can be derived from all these various poplars. All that is left here is hopefully our solution which contains our glucose, that we can now move forward and analyse throughout high performance liquid chromatography. And finally, this is a graphical representation of the glucose that we have derived. The size of the peak indicates how much sugar we have on a given sample.”

Richard J. Murphy: “Poplars are carbon storage, they are high growth rate. And if we can get an easy conversion, if we can facilitate the conversion of biomass into the biofuel, we can end up with some very, very good greenhouse savings compared to gasoline; very significant ones, perhaps 90% savings over gasoline is achievable here. Which means we can effectively de-carbonise large parts of the transport sector.”

Research to break the cellulose barrier continues, as European scientists promise a new dawn for biofuels… with poplars as key suppliers.

For more information see
www.energypoplar.eu