The use of renewable resources for producing bioplastics and biofuels leads to lower emissions of greenhouse gases and uses less fossil energy than the production of their plastic and fuel counterparts in the petrochemical industry. At the top of the list for the Netherlands are all bioplastics (particularly the biodegradable bioplastic PLA) made from sugar beet, on which savings of 65% can be made when compared with fossil energy consumption. This study did not take the possible change in land use into account. The full story is available in the (Dutch) Groene Grondstoffen booklet entitled ‘Duurzaamheid van biobased producten’ (The sustainability of biobased products) by Wageningen UR Food & Biobased Research, which is published today.
Scientists from Wageningen UR and Utrecht University studied the sustainability aspects of bioplastics and bioethanol of five different crops used as renewable resources: Dutch wheat, grain maize, sugar beet and Miscanthus grass, and cane sugar from Brazil. The bioplastics and biofuels were compared with similar products from the petrochemical industry. The scientists used a lifecycle analysis (LCA) to calculate the emission of greenhouse gases and the fossil energy consumption. This sustainability evaluation covers the entire production process, from sowing the crops via transport and processing through to the actual production of biomaterials and biofuels. The evaluation also takes account of the use or non-use of the residual materials, such as wheat straw and beet pulp, as possible sources of energy.
This study is the first time that real data from crop cultivation have been linked to data on chemical production. The information and data came from Plant Research International, part of Wageningen UR, and Utrecht University respectively.
Focusing the analysis
The current standard lifecycle analysis calculates sustainability in terms of greenhouse gases per ton of product. “In addition, we have made another calculation per hectare of agricultural land. The results of these two analyses show huge differences,” says Harriëtte Bos, programme manager of Biobased Economy at Food & Biobased Research. “These findings stress the importance of focusing the analysis on the specific situation. They also show that the points of departure from each sustainability study should be clearly defined when comparing different studies.”
Results for the Netherlands
Replacing fossil plastic or fuel with a biobased counterpart led to a reduction in greenhouse gas emission in all the products analyzed. These results show that in the Netherlands, when compared with petrochemical polyethylene, the largest reduction in greenhouse gas emissions per ton of product can be achieved by using wheat, maize and Miscanthus grass if, alongside producing biopolyethylene, the residual materials are transformed into energy.
“Two factors were not taken into account in these findings. It takes a lot more land to produce a ton of fermentable sugar from wheat, maize and Miscanthus grass than from sugar beet”, according to Bos. “You need 0.31 hectares per ton of bio-polyethylene for sugar beet and 0.68 hectares per ton of product for wheat.” This is an important factor in a country like the Netherlands, where the area available for agriculture is limited.
“The second factor is that you need around 2.5 times more fermentable sugar to produce bio-polyethylene than to produce PLA (polylactic acid)”, explains Bos, “so if you want to produce as much bioplastic as possible in the smallest area of land, then at 500 GJ per hectare, PLA made from sugar beet is the most economical option when compared with the fossil alternative plastic PET (polyethylene terephthalate).”
This study was commissioned by the interdepartmental programme management board of Biobased Economy at the Ministry of Economic Affairs, Agriculture & Innovation.
Wageningen UR, press release, 2011-03-29.