With the surge in bio-based activities around the globe, a new concept called bio-refining starts to emerge. IEA Bioenergy Task 42 on Biorefineries defines biorefining as “the sustainable processing of biomass into a spectrum of marketable products and energy”. A bio-refinery combines/integrates a series of biomass conversion technologies to produce a range of products and (base-)materials, such as food, feed, chemicals, materials, oil, gas, heat and/or electricity. The concept is similar to a conventional oil-refinery where multiple petroleum products and fuels are produced.
A bio-refinery combines a series of technologies, such as for the production of bio-diesel, bio-ethanol, bio-plastics, bio-CHP, biogas (1, 2, 3, 4), bio-char, and bio-polymers, etc. to form an integrated plant that aims to optimize the biomass conversion process in such a manner that the highest added value can be ‘extracted’ from the renewable biomass feedstock used.
The specific technological configuration of a biorefinery can differ from case to case as it is highly dependent on local circumstances, such as agricultural practices and climatic variations. Such factors determine the type, quality and quantity of the feedstock that is available for processing. Possible feedstocks that can be used in a bio-refinery are, sugar beets, black liquor, wheat, corn, wood, agricultural residues, sugar cane, surplus food, straw, aquatic biomass, but also the biomass fraction of municipal and other types of waste (MSW), etc. The main product groups of a biorefinery are: chemicals, biofuels, electricity & heat, materials (fibres, starch, wood), food and feed, minerals, CO2, and H2O.
Aside from mechanical biomass cultivation and processing technologies (e.g. harvesting, milling and pressing), there are two main routes for bio-refining.
1) Technologies like a.o. pyrolysis and gasification are so-called thermochemical processes. Here a combination of heat, pressure in the absence of oxygen cause for the chemical breakdown of the biomass feedstock into a number of biocomponents, such as cellulose, hemicellulose, lignin and extractives. These bio-components can then be further processed into commercial products.
2) (Bio)chemical conversion uses chemicals and/or microorganisms (e.g. enzymes) to establish the desired breakdown process of the biomass feedstock into various components. Relevant technologies here are a.o. hydrolysis, fermentation and digestion.
A clear view on what type of technology configuration constitutes the ideal or optimal biorefinery is still unclear as most of the foreseen sub-technologies are in the R&D stage or pre-commercial. The most flexible technological biorefinery concepts that can produce multiple marketable outputs from diverse feedstocks are likely to have a competitive advantage as production can be optimized to produce that set of products with the highest added value. In terms of technological feasibility this would require a sufficient degree of process integration.
A white paper by D. King, et al., ‘The Future of Industrial Biorefineries’ for the World Economic Forum (2010) stresses the importance of certain necessities for successful development and deployment of biorefineries.
Improving feedstock yield and biomass composition for optimal conversion efficiency is seen as a necessary to the success of future biorefineries. Adapting operational aspects such as plant genomics, breeding programs and chemical engineering (of the feedstock so that, sugar content, drought/temperature resistance are improved) are important for effective operation. This includes the ongoing development of more efficient enzymes and microbial cell factories.
Cost-effective and efficient processing and logistics of the biomass feedstock is another crucial operational necessity. Increasing feedstock density with briquetting and pelletizing techniques allows for more cost-effective transport as excess mass (such as water) is removed from the cargo-load. High quality feedstock preservation and storage techniques to prevent decay and quality reduction could are important factors for improving process efficiency.
Simply stated the concept of a biorefinery is not only dependent on the effective technological integration of a series of thermochemical and biochemical conversion technologies, but requires a range of facilitating technologies and processes (including land and forestry management processes) to be in place for effective development and deployment.
According to R. van Ree and B. Annevink (2007) there are several different biorefinery concepts possible. Conventional biorefineries (CBRs) for instance are already existing food production and processing activities. Examples of CBRs are the sugar, starch and vegetable oil industry. The so-called green biorefinery (GBR) assumes processing fresh (wet)biomass, such as green grass, lucerne and clover crops. Pressurization of wet biomass results in a fibre-rich press cake and a nutrient-rich press juice. Whole crop biorefineries (WCBR) assumes mechanical separation of the food-grade fraction (i.e. rice, wheat, etc.), whereas the residual part (e.g. straw) is further processed in the petrochemical industry in a ligno-cellulosic feedstock biorefinery platform (LCFBR). A number of other biorefenery concepts with an assessment of the development status are provided in the figure below.
Source: R. van Ree and B. Annevink (2007)
As a biorefinery cannot be seen as a single technology but an integrated set of individual technologies it is difficult to determine the exact status of the technology. For a more precise understanding of the status of individual biomass technologies one is referred to, bio-diesel, bio-ethanol, bio-plastics, bio-CHP, biogas (1, 2, 3, 4), bio-char, and bio-polymers.
For those stakeholders that are considering implementing, bio-based polymer production in the chemicals sector, the technology could contribute to:
- A reduction of fossil-based energy consumption, and a relative reduction of fossil fuel import dependence, in case of large-scale bio-energy production,
- A reduction of greenhouse gas emissions (dependent on specific life cycle impact),
- A reduction in the discharge of process related waste streams, as more most elements of the biomass feedstock are processed and ‘re-used’ for commercial purposes, either for the plants’ own energy consumption or for new product markets (i.e. chemicals, pharmaceutics, etc.)
- A potential increase in employment in the agriculture/forestry sector (e.g. harvesting, storage), and possible positive rural development and income effects,
- A potential positive industrial competitiveness and innovation impact (i.e. techno-business cluster development) with ongoing demonstration and deployment.
Despite the potential positive impacts of biorefinery development and deployment the sustainability of future biorefineries is highly dependent on the way in which they are implemented. Flawed technological biorefinery designs or processes and/or non-sustainable agricultural, forestry or aquatic management practices could also lead to unwanted side-effects, for instance when land-use change or soil degradation (e.g. nutrient loss) issues are not dealt with.
In order to address such issues various market stakeholders are trying to establish certification schemes that aim to verify and ensure sustainable biomass practices based on a set of sustainability criteria.
The impact of bio-based products from biorefineries on the climate is strongly dependent on the type of feedstock its land-use impact and the efficiency of the conversion process. Assessing the GHG emissions of these products using a full life cycle analysis critically depends on the inclusion of emissions caused by land-use change.
In Directive 2009/28/EC of the European Parliament and the council of 23 April 2009 on the promotion of the use of energy from renewable sources the greenhouse gas (GHG) emission savings typical and default values for a number of assumed biofuel production processes is calculated based on a specific methodology (see figure below). The data shows that biofuel production processes could contribute significantly to GHG emissions reduction as compared to fossil-based reference processes. However, fundamental to the methodology used is that for the selected biofuel production processes no net GHG impact from land-use change has been assumed. Including, this GHG-impact category might significantly alter the presented values. Specific land-use change impact analysis is a complex matter given the large differences in soil type and characteristics.
|Biofuel production pathway||Typical greenhouse gas emission saving||Default greenhouse gas emission saving|
|sugar beet ethanol||61%||52%|
|wheat ethanol (process fuel not specified)||32%||16%|
|wheat ethanol (lignite as process fuel in CHP plant)||32%||16%|
|wheat ethanol (natural gas as process fuel in conventional boiler)||45%||34%|
|wheat ethanol (natural gas as process fuel in CHP plant)||53%||47%|
|wheat ethanol (straw as process fuel in CHP plant)||69%||69%|
|corn (maize) ethanol, Community produced (natural gas as process fuel in CHP plant)||56%||49%|
|sugar cane ethanol||71%||71%|
|rape seed biodiesel||45%||38%|
|palm oil biodiesel (process not specified)||36%||19%|
|palm oil biodiesel (process with methane capture at oil mill)||62%||56%|
|waste vegetable or animal oil biodiesel||88%||83%|
|hydrotreated vegetable oil from rapeseed||51%||47%|
|hydrotreated vegetable oil from sunflower||65%||62%|
|hydrotreated vegetable oil from palm oil (process not specified)||40%||26%|
|hydrotreated vegetable oil from palm oil (process with methane capture at oil mill)||68%||65%|
|pure vegetable oil from rape seed||58%||57%|
|biogas from municipal organic waste as compressed natural gas||80%||73%|
|biogas from wet manure as compressed natural gas||84%||81%|
|biogas from dry manure as compressed natural gas||86%||82%|
Typical and default values for biofuels if produced with no net carbon emissions from land-use change, source: EC, 2009 (adapted).
Currently (august, 2010) there are 697 biomass-energy projects in the CDM pipeline that all have provided calculations on project specific GHG emission reductions. The calculation methodologies used in these CDM projects can be used as a basis for own GHG emissions impact assessments. Specific life cycle analysis studies of the GHG-impact of biomass-chemicals projects or bio-refinery concepts are scarcer and not widely available.
The cost of production of bio-based products and, in particular, the investment needed for infrastructure and supply will have a direct bearing on their success as an alternative to fossil-based products. An efficient biorefinery will ensure cost minimization and a cost competitive end product. At present, efficiency is difficult to define since an efficient biorefinery is still a concept. However, if one describes biorefinery efficiency in terms of utilizing local resources and the existing infrastructure, maximizing biomass-to-product conversion rates, ensuring flexibility in the products produced by the refinery and streamlining supply chains, then it is clear it will have a large impact on the economic viability of biorefineries.
Additionally, optimizing the biorefinery’s product portfolio so as to be able to sell high value added bio-based products, such as chemicals, materials and food-pharmaceutical-cosmetic products as well as bio-commodities such as liquid or gaseous bioenergy and heat and power. Producing such a broad portfolio can significantly improve the economics of the biorefinery concept.
Given the R&D and demonstration status of most of the biorefinery technologies are still not fully competitive with the competing fossil-based technologies, as the required investment cost and operational expenses are too high, either due to a higher cost of finance (i.e. technology risk) or due to unfavorable competitive conditions (i.e. fossil subsidies and/or no policy geared towards internalizing environmental costs associated to production processes).
- IEA Bioenergy Task 42 on ‘Biorefineries’, http://www.biorefinery.nl/ieabioenergy-task42/
- Various technology descriptions on www.climatetechwiki.org
- R.W.R. Zwart, 2006, ‘Biorefinery The worldwide status at the beginning of 2006’
- EC, 2009, ‘Directive 2009/28/EC of the European Parliament and the council of 23 April 2009 on the promotion of the use of energy from renewable sources’
- R. van Ree and B. Annevink, 2007, ‘Status Report Biorefinery 2007’
- D. King, et al., 2010, ‘The Future of Industrial Biorefineries’ white paper for the World Economic Forum