Biomass: green gold at our fingertips

In the race towards renewable resources, biomass could well have an important role to play. Biomass includes organic matter derived from living organisms, particularly plants, which have more to offer than you might think. Patrick Navard is a researcher in materials at Mines ParisTech. Following his presentation at the “Materials: realities and new frontiers” symposium, organized on March 30-31, 2016 by Institut Mines-Télécom, we asked him to shed some light on the issues and limitations relating to the use of biomass.

Will green gold eventually replace black gold? Will oil’s overwhelming domination be challenged by the biological resources all around us? The Brent Crude oil price per barrel, which has been falling for over a year, seems to leave little hope for any competition. Yet biomass — all organic matter of animal and plant origin — could very well put up a fight. The reasons for its appeal are indeed more complex than issues of economic competition in the energy and materials markets, sectors predominantly supplied by hydrocarbons and their derivatives. Whether oil prices are up or down, it nevertheless remains a “limited resource, from which we will need to break free eventually,” says Patrick Navard, a researcher in bio-sourced materials at Mines ParisTech. This desire to find alternative solutions is also motivated by the growing appeal among citizens for eco-labeled products. “We all want to leave a cleaner planet for our children,” adds this expert in bio-inspired materials, putting environmental issues back at the heart of the matter. This dimension is already integrated by brands into their product marketing, in which they boast about compliance with countless ISO standards and ever lower CO₂ emissions.

While these driving forces for an ecological transition require massive efforts over a relatively long period of time — a new vision of society is rarely accepted immediately and unanimously — they are supported by more practical aspects. Biomass is not simply a replacement solution: it is also a catalyst for innovation. “Certain products obtained from renewable resources are much better than those manufactured using fossil resources,” Patrick Navard argues. “A good example of this is cars: composite materials that use natural fibers are 15 to 20% lighter than those made with glass fiber.” This boost in performance from the bio-sourced material, in this case, is directly accompanied by a decrease in shipping and handling costs and, eventually, a reduced carbon footprint — a lighter car that emits less CO₂ per kilometer.

Biomass – an opportunity for materials

The materials industry is one of the sectors that could, like energy, be greatly impacted by this transition. Polymers, which are components of plastic materials, are in the vanguard of this change. But there is still a long way to go. As Patrick Navard likes to say: “The use of biomass to develop plastic materials is developing rapidly, but it started out at a very low level.” Bio-sourced polymers currently only represent 0.1% of the polymers used around the world. And yet their properties are not that different. In fact, they are similar. “Whether we are talking about using oil or biomass to produce polymers, in the end it boils down to the same thing,” the researcher explains. Because oil, after all, is nothing other than biomass that has been buried in the ground and digested by the earth through chemical and biological processes over millions of years.

The global production of plastic materials amounts to 300 million metric tonnes. The use of biomass as a polymer source could therefore increase considerably to meet the growing demand (250 million in 2009, 204 million in 2002).

In Patrick Navard’s opinion, making any kind of polymer using renewable resources is perfectly conceivable: “The plant fibers must simply be broken down to form chemical building blocks, thus reproducing what nature does over a much longer period of time.” Such products already exist: polyethylene, for example, can be synthesized using cane sugar. Likewise, cornstarch can initiate the synthesis of polylactic acid, a biodegradable polymer used for food packaging. Another highly prized natural molecule is already used in industry: cellulose. It represents over 50% of the plant biomass and regularly supplies pulp mills.

Biomass refineries

Yet a problem remains in all these syntheses initiated by natural molecules: once the desired substance has been extracted, what is done with the remainder of the used plant matter? Cellulose is a major component of plants, but it is not the only molecule. The others, like lignin and hemicellulose, are mostly burned in current industrial practices. And yet lignin plays an important role in the rigidity of plants and could be recovered. “Lignin is the most abundant source of aromatic compounds on earth, and yet it is currently almost completely untapped, while industry uses many synthetic aromatic substances, which are particularly polluting,” regrets Patrick Navard. The lignin molecule present in wood could therefore be a precursor to the development of products that are in high demand. However, the researcher cautions that “Many research projects around the world are trying to exploit lignin and, so far, with little success, because it is a complex molecule.”

This leaves us with the idea of recovering compounds currently considered as waste. This principle is at the heart of the biorefinery concept. It involves modeling the oil processing procedures, in which the various molecules composing the crude oil are separated: the heavy fractions are used for bitumen and the lighter fractions become solvents for the chemical industry. Nothing is wasted from this precious black gold. So why discard the biomass by-products? This example illustrates the advantages of waste recovery: when Miscanthus, a herbaceous plant, is harvested, an initial sifting procedure removes the sediments. Rather than discarding these sediments, “they can be used in the development of composite materials,” Patrick Navard explains.

In addition to the sediments obtained from screening, the Miscanthus plant is used to reinforce composite materials. The material’s mechanical properties vary according to the chosen species.

Environmental impact and land management

The prospects presented by biorefineries must also be tempered with caution. Though their development may be synonymous with more environmentally sustainable production, since it is based on renewable resources, this does not necessarily mean the environmental impact will be reduced. “If highly polluting chemistry must be used to recover the plant’s resources, the environmental impact is not reduced at all,” Patrick Navard cautions. The researcher illustrates these remarks with a comparative impact study carried out at two cellulose thread factories owned by the same company, one in Austria, and the other in Indonesia. Despite following the same manufacturing process, the Austrian factory was less polluting. The reason for this was the distance from the forest from which the trees were obtained. In Indonesia, the forest was located several hundred kilometers away, significantly increasing the carbon footprint from the transportation of the wood, whereas the Austrian factory used a more local supply. “This problem does not exist for the oil industry, since it does not cost a lot to push crude oil through a pipe. But wood can’t be transported in the same way,” Patrick Navard explains.

The issue of geographical location does not just apply to biorefinery sites. With the use of biomass comes the problem of land being used for purposes other than agri-food production. This issue already arose several years ago with the cultivation of crops for biofuel, which led to highly questionable results. Indeed, numerous problems exist – from humanitarian disasters caused by the increased price of corn, to the simple impossibility, given the yields, of allocating enough land. This possibility of producing first-generation biofuels is flawed for many reasons, and is not ethical. “The problem is different for materials,” explains Patrick Navard. “We do not need to produce as many crops in this case. While fuel constitutes one of the biggest oil products, materials only use the equivalent of a few percentage points of crude oil.” Therefore, less land is required to redistribute the demand for materials to biomass than would be required to meet the demand for fuel. In addition, the cultivation of crops used for dual purposes can be envisioned, combining food purposes with the production of resources for the development of materials.

Convincing farmers and industrialists

Yet there is still an obstacle to the development of biorefineries and the use of biomass: their appeal to farmers and industrialists. “Farmers will not go into this business unless they are certain they will be able to sell their crops, and industrialists will not develop these products unless they are sure they can buy at a reasonable price,” explains Patrick Navard. The structuring of these sectors is therefore the key issue. In Germany, agreements have been made between farmers and manufacturers, enabling the launch of these initiatives. But not all the initiatives are successful. In South America, the industry based on the Curauá plant did not develop to the expected extent due to a lack of stability: the presence of only one distributor on the market cannot guarantee the security of production. In France, Patrick Navard assures us that initiatives are emerging, but adds that things are slow and difficult at times: “There’s a lot of red tape to get through, at the regional, departmental and municipal levels.” Yet time seems to be running out. On the one hand, oil resources are diminishing, and prices will increase due to the ever-growing demand, which will speed up the ecological and environmental transition. But on the other hand, CO₂ emissions are skyrocketing, leaving our societies with even less time to limit the irreversible impacts of our activities.

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