To counteract global warming and the subsequent climate change there is an urgent need to transform our production and consumption models and become more sustainable. In other words, we need to change the prevailing economic model for a circular bio-economy that substitutes fossil based raw materials with renewable organic based ones.
Thus, in the future –at least ideally– the economy will boost the use of raw materials of biological origin instead of other materials of fossil origin. In that not-so-far-away future, industries will turn to trees for energy and as an alternative to plastics. We will see new markets emerge, in addition to traditional ones, such as pulp and paper, whilst new innovative uses for wood are researched and developed. This implies a huge demand of biomass that can be met from short rotation tree crops, such as poplar, grown specifically for industrial needs.
Poplar woods have always existed in Europe, but it wasn´t until some decades ago that the concept “short rotation tree” caught the attention of growers and the industry alike.
Poplar is one of the most efficient trees in terms of sustainability. It is one of the fastest growing trees in the world. In Europe, one cubic meter of lumber can be produced, on average, in 15 years. Compared to other trees like oak, for example, that take more than 100 years… poplars are very fast.
And, as all fast-growing trees, poplar has an excellent capacity to purify the air by capturing CO2 and storing it in the biomass of the trees. In one year, a hectare of poplar can capture 11 tons of CO2. But what does that mean? Well, one tonne of CO2 is equivalent to the average carbon dioxide emissions of one passenger in a return trip from Paris to New York. So, in one year a hectare of poplar would capture the CO2 equivalent to 11 people traveling from a Paris to New York and back. What is more, the carbon dioxide contained in the grown trees remains stored in the logs and in the panels made from them.
Poplar trees also purify water as they act as green filters absorbing nitrates and sediments. Contrary to some beliefs, a poplar plantation does not need more water than other crops such as a cornfield or an oak forest of similar dimensions. Among other benefits, poplar trees combine well with agroforestry and can also be planted in otherwise useless lands thus optimizing land use.
As for its industrial use potential, poplar offers a series of features that make it right for the economy of the future. Poplar produces a very versatile wood, with an excellent ratio between specific weight and mechanical features that make it suitable for the furniture sector as well as for the plywood industry, where the lightness and fair colour of its wood logs allows obtainment of wide white wood sheets. On the other hand, despite its resistance, poplar wood is mild, and therefore easy to work with, therefore reducing tool consumption too.
As for biofuels, in recent years the University of Washington as well as other institutions have been testing the potential of younger poplar trees for biofuel production using the method known as coppicing. These younger trees, known as poplar coppice, are planted closer together than in a normal poplar tree plantation and can be harvested more frequently, that is in two or three years, instead of the 15-20 usual cycle. The trees are cut in a way that allows more branches to sprout from the stump after each harvest, using the same root system for over two decades.
The results of UW’s research, that attempted to convert the entire poplar coppice, that is bark, leaves and stems, into bio oil and ethanol, were published in 2017 in the journal Chemistry and Engineering. These results suggest poplar coppice have the potential to create alternative and competitive fuels suitable for a new bio-based economy.