Biomass by numbers

Theoretically, using biomass energy sources is very attractive, and is carbon-neutral and renewable as well. This is why wood-based biomass is already a commercial technology of much interest to policy-makers. However, the theoretical basis for clean biomass energy remains exactly that – theoretical. "There are three questions that have never been answered about energy from wood-based biomass," explains Reinhart Ceulemans: "Is it efficient? Is it economically profitable? And,above all,does it truly save on greenhouse gas emissions?" To answer these questions, he and his team from Belgium's University of Antwerp are implementing the POPFULL project with a five-year ERC Advanced Grant to undertake a complete life-cycle analysis (LCA) for a biomass plantation. They are measuring all inputs and outputs along with the costs and benefits they have for the environment.

In Flanders' fields (and forests)

Close to Ghent, the team has established a mixed plantation of fast-growing poplar and willow tree varieties covering over 18 hectares. They are investigating short-rotation coppicing (SRC) where the trees are cut back to the ground every two years and their stems and branches harvested, chipped and used to generate energy.

the research will cover two harvesting cycles in 2012 and 2014. As a vital part of the LCA, all inputs and outputs from the SRC processare measured, such as the fuel used by plantation machinery, the greenhouse gas (GHG) emissions from biomass combustion and the energy produced.In addition, the eco-system carbon balance is measured, meaning the GHG inflows and outflows in the plantation, including CO2, CH4 and N2O and others. "By combining the SRC process measurements with those on the eco-system we will arrive at a full LCA carbonbalance for short-rotation coppicing and a quantitative result on its contribution to global warming," explains Ceulemans.

new tools and tall towers

"The measurement of greenhouse gas fluxes is the key element in our work – it is only recently that the new tools and techniques to do this have become available," says Ceulemans. Among the rows of trees is a tall mast supporting the three-dimensional anemometer and highly-sensitive gas analysers. "We continuously measure the wind speed in three directions and the GHG concentrations in the atmosphere to obtain the net fluxes into and out of the plantation. The difference is the uptake of gases by the trees, mainly through photosynthesis. The instruments are highly sensitive, we can see photosynthesis dropping off as night falls and even the rise in CO2 when we have large groups of visitors."

Much of the valuable work on measuring GHG fluxes was undertaken by Dr Donatella Zona, a key researcher in the team, supported by a Marie Curie Grant. "This is a unique plantation, the first in the world with the equipment to measure the full greenhouse gas balance and thus produce a full life cycle analysis," explains Ceulemans, "So we have seen a lot of interest – even National Geographic magazine has made a documentary on the project."

Harvesting results

"After one rotation we have seen that we get twice the energy out as is put in, and the second rotation will be better; so the plantation is efficient. For greenhouse gases we still need the results from the second rotation – so far the process is not fully carbon neutral yet, but we are saving considerable amounts of greenhouse gases as compared to fossil fuels," says Prof.Ceulemans. "However, we suspect that, without subsidies, SRC will only be economic over a period of 20 years or so. Yet, many energy sources are subsidised, so this is a matter of policy rather than simple economics," he explains.

"Looking more widely, when POPFULL is complete we will have the hard numbers that will allow science- and evidenced-based policy-making to help biomass find its right place in the energy mix of the future."

- Source: Prof.dr. Reinhart Ceulemans
- Project coordinator: University of Antwerp, Belgium
- Project title: System analysis of a bio-energy plantation: full greenhouse gas balance and energy accounting
- Project acronym: POPFULL
- POPFULL project website
- FP7 funding programme (ERC call): Advanced Grant 2008
- EC funding: EUR 2 500 000
- Project duration: five years

- National Geographic documentary (nl/en):
- English
- Netherlands

- Selected publications:
- Njakou Djomo S., El Kasmioui O. and Ceulemans R. (2011) Energy and greenhouse gas balance of bioenergy production from poplar and willow: a review. Global Change Biology Bioenergy, 3: 181-197
- Broeckx L.S., Verlinden M.S. and Ceulemans R. (2012) Establishment and two-year growth of a bio-energy plantation with fast-growing Populus trees in Flanders (Belgium): Effects of genotype and former land use. Biomass and Bioenergy, 42: 151-163
- El Kasmioui O. and Ceulemans R. (2012) Financial analysis of the cultivation of poplar and willow for bioenergy. Biomass and Bioenergy, 43: 52-64
- Njakou Djomo S. and Ceulemans R. (2012) A comparative analysis of the carbon intensity of biofuels caused by land use changes. Global Change Biology Bioenergy, 4: 392-407
- Berhongaray G., El Kasmioui O. and Ceulemans R. (2013) Comparative analysis of harvesting machines on an operational high-density short rotation woody crop (SRWC) culture: one-process versus two-process harvest operation. Biomass and Bioenergy, doi:10.1016/j.biombioe.2013.07.003
- Njakou Djomo S., El Kasmioui O., De Groote T., Broeckx L.S., Verlinden M.S., Berhongaray G., Fichot R., Zona D., Dillen S.Y., King J.S., Janssens I.A., Ceulemans R. (2013) Energy and climate benefits of bioelectricity from low-input short rotation woody crops on agricultural land over a two-year rotation. Applied Energy, 111: 862-870
- Verlinden M.S., Broeckx L.S., Wei H. and Ceulemans R. (2013) Soil CO2 efflux after land use change to a bioenergy plantation with fast-growing Populus trees – influence of former land use, inter-row spacing and genotype. Plant and Soil, 369: 631-644
- Verlinden M.S., Broeckx L.S., Zona D., Berhongaray G., De Groote T., Camino Serrano M., Janssens I.A., Ceulemans R. (2013) Net ecosystem production and carbon balance of an SRC poplar plantation during its first rotation. Biomass and Bioenergy, 56: 412-422.
- Zona D., Janssens I.A., Aubinet M., Gioli B., Vicca S., Fichot R., Ceulemans R. (2013) Fluxes of the greenhouse gases (CO2, CH4 and N2O) above a short-rotation poplar plantation after conversion from agricultural land. Agricultural and Forest Meteorology, 169: 100-110.