{"id":18863,"date":"2014-01-16T03:09:40","date_gmt":"2014-01-16T01:09:40","guid":{"rendered":"http:\/\/www.cell.com\/trends\/biotechnology\/abstract\/S0167-7799(13)00227-8"},"modified":"2014-01-15T16:17:44","modified_gmt":"2014-01-15T14:17:44","slug":"sustainability-considerations-integrated-biorefineries","status":"publish","type":"post","link":"https:\/\/renewable-carbon.eu\/news\/sustainability-considerations-integrated-biorefineries\/","title":{"rendered":"Sustainability considerations for integrated biorefineries"},"content":{"rendered":"

Integrated biorefineries have the potential to contribute towards sustainable production of transportation fuels, energy, and chemicals. However, because there are currently no commercial biorefining plants in operation, it is not clear how sustainable they really are. This paper sets out to examine key issues associated with biorefining that should be considered carefully along the whole supply chain to ensure sustainable development of the sector.<\/strong><\/p>\n

Sustainability<\/h3>\n

Sustainable development is an approach that strives to satisfy human needs in an economically viable, environmentally benign, and socially beneficial way. There are many sustainable development issues, or, for short, sustainability issues that must be considered when evaluating whether a product or human activity is sustainable. These include, for example, environmental impacts such as global warming, acidification, and loss of biodiversity, economic aspects such as costs and profits, and social concerns such as employment, health, and human rights. The sustainability of a product or activity can be measured quantitatively and\/or qualitatively by estimating or assessing the economic, environmental, and social impacts.<\/p>\n

Integrated biorefineries<\/h3>\n

Integrated biorefineries use various biofeedstocks to produce biofuels, energy (electricity and heat), and chemicals. Typically, all of the heat and some of the electricity generated by the refinery are used for its operation, and the rest of electricity is sold to the grid. Owing to issues such as climate change, security of energy supply, and increasing costs of fossil fuels, the main driver for developing integrated biorefineries is the production of biofuels for transportation, with the co-products (electricity and chemicals) helping to maximize value derived from feedstocks.<\/p>\n

Biorefineries, their feedstocks, and products can be classified as first, second, or third generation [1<\/a>]. First-generation feedstocks are food crops such as corn (maize), wheat, and sugar cane. Currently, most of the global biofuel production consists of first-generation ethanol, which represents over 80% of liquid biofuels by energy content [2<\/a>]. This has led to competition with food production, both in terms of land use and reduced supply of food crops, pushing up food prices in some countries. The focus is now shifting from first-generation feedstocks to second- and third-generation feedstocks for use in integrated biorefineries. Second-generation feedstocks are lignocellulosic materials and include energy crops (e.g., poplar and miscanthus) and wastes (e.g., agricultural, forestry, and municipal waste). Third-generation feedstocks consist mainly of microalgae. Waste CO2<\/sub> from power plants or elsewhere could also be used as feedstocks in the future.<\/p>\n

An integrated biorefinery can use a biochemical or thermochemical route, or a combination of both, to process the feedstocks into useful products. The biochemical route uses microorganisms (e.g., yeast) and enzymes in biological processes such as fermentation to process the biomass, whereas the thermochemical route relies on heating the feedstock to temperatures between 300\u00b0C and 1000\u00b0C with little or no oxygen. Each route will have to overcome a range of technological issues before it can become a commercial reality, including the flexibility to use different types of feedstocks, the efficient use of feedstocks, and the successful scaling-up from pilot- to large-scale plants [3<\/a>]. In addition to technological issues, integrated biorefineries face a number of sustainability challenges \u2013 environmental, economic, and social \u2013 that must be considered on a life-cycle basis. This means that the whole life cycle of a biorefinery system must be considered, from the cultivation and harvesting of biomass (if applicable), to its collection and transportation to the plant, its conversion to fuels, energy, and chemicals, and their consumption by end users. This is necessary to avoid shifting sustainability impacts from one part of the supply chain to another \u2013 for example, reducing greenhouse gas (GHG) emissions from the refinery only to increase them through transportation of feedstocks to the refinery. Evaluation on a life-cycle basis is also required by various legislative acts related to biofuels, including the EU Renewable Energy Directive [4<\/a>] and the US Energy Independency and Security Act [5<\/a>].<\/p>\n

The first commercial second-generation biorefining facility is expected to come online in late 2013 in the United States [6<\/a>]. Therefore, I will focus on second-generation biorefineries for the following discussion of key sustainability issues in the supply chain.<\/p>\n

Environmental considerations<\/h3>\n

Greenhouse gas emissions<\/h3>\n

One of the main drivers for biofuels and integrated biorefineries is their potential to save GHG emissions compared to fossil fuels. This is illustrated in Figure 2<\/a>, which compares the life-cycle GHG emissions of ethanol from different biofeedstocks to petrol. As indicated, the GHG emissions from ethanol produced in an integrated biochemical refinery from second-generation feedstocks are negative, indicating a saving in GHG emissions ranging from \u22127 g CO2<\/sub> eq.\/MJ of fuel for wheat straw to \u221219 g CO2<\/sub> eq.\/MJ for poplar (T. Falano, PhD thesis, University of Manchester, 2012). This is due to the \u2018credits\u2019 for the co-products \u2013 in this case, electricity, lactic acid, and acetic acid \u2013 whereby their GHG emissions, which would have been generated by their production in conventional plants from fossil resources, are subtracted from the biorefinery emissions.<\/p>\n

In some cases, as in this example, the credits are greater than the actual emissions from the plant, hence the negative value, indicating that these emissions have been avoided or saved. This means that, compared to petrol, a saving of up to 104g CO2<\/sub> eq.\/MJ of fuel could be achieved from ethanol produced by this integrated biorefinery. By comparison, the lowest GHG emissions from first-generation ethanol are from Brazilian sugar-cane ethanol, which saves up to 65g CO2<\/sub> eq.\/MJ on petrol \u2013 this is 1.6 times lower than the saving from ethanol from the integrated biorefinery. In the worst case \u2013 ethanol from US corn \u2013 there are no GHG savings; in fact, its emissions are 1.5 times higher than from petrol [7<\/a>]. This is due to the emissions of N2<\/sub>O from the application of fertilizers during corn cultivation, which outweigh the global-warming potential of CO2<\/sub> emissions from petrol combustion.<\/p>\n

Land-use change<\/h3>\n

Additional GHG emissions are generated if land is converted from its present use for the cultivation of biofuel feedstocks. This is relevant to energy crops and potentially microalgae, and might lead to both direct and indirect land-use change (LUC). The former involves conversion of land from its current use to cultivate biofuel feedstocks, and the latter is related to the displacement of existing agricultural activity (e.g., food crops) due to the cultivation of biofeedstocks. As a result, LUC is often associated with a change in land cover that leads to a change in carbon stocks, which in turn generates GHG emissions. In some cases, LUC will result in GHG emissions that are large enough to outweigh the GHG savings gained from producing biofuels instead of fossil fuels. For example, when deriving ethanol from miscanthus (Figure 2<\/a>), conversion of forest land in the United Kingdom to the cultivation of miscanthus releases 20 t CO2<\/sub> eq.\/ha\/year [8<\/a>], which increases the GHG emissions of ethanol from \u221211 to 310g CO2<\/sub> eq.\/MJ. This is 3.6 times higher than the emissions from petrol. Therefore, LUC is a crucial factor that must be taken into account when estimating GHG emissions from biofuels.<\/p>\n

Biodiversity<\/h3>\n

Loss of biological diversity can occur when forests and grasslands are converted to cultivate biofuel crops. For example, large mono-crop areas attract only a limited number of species. However, if degraded lands are restored for biofuel crop production, biodiversity can improve.<\/p>\n

Forest and agricultural residues are expected to have lower negative impacts on biodiversity than energy crops [9<\/a>]. However, the removal of agricultural residue from fields might increase weed growth, which could necessitate the increased use of herbicides, thus affecting local biodiversity as well as environmental pollution. Replacement of native forests with mono-crop plants, particularly more invasive species, could also result in a significant reduction in biodiversity. For example, eucalyptus, some miscanthus species, and switchgrass all exhibit some features of invasiveness [10<\/a>].<\/p>\n

Biodiversity loss can also occur owing to LUC. For example, if set-aside land in Europe is used to grow biofuel crops, impacts on biodiversity will need to be evaluated carefully because some of these set-aside areas can be more biodiverse than farmlands [1<\/a>].<\/p>\n

Water use<\/h3>\n

Water use varies widely with feedstock type. For example, feedstocks from waste require little or no water, whereas energy crops such as jatropha, eucalyptus, switchgrass, and miscanthus generally have higher water demand than arable crops owing to longer seasonal growth and transpiration rates [9<\/a>]. This can be an issue in water-stressed regions owing to the need for irrigation. For example, cultivation of jatropha in Bangalore requires 1311mm\/year of irrigation water, leading to the total water footprint of 58700l\/l diesel [11<\/a>]. Conversely, water use by biorefineries is relatively modest: for example, producing biodiesel requires 1\u20133l\/l of fuel [9<\/a>].<\/p>\n

Other environmental impacts<\/h3>\n

Further environmental impacts associated with integrated biorefineries and their products include acidification, eutrophication, human toxicity, and eco-toxicity. The agricultural stage is the major contributor to these impacts owing to air emissions of ammonia and leaching of nutrients from fertilizers, as well as air emissions from the use of fuel in agricultural machinery. The biorefinery also contributes to these impacts owing to emissions of SO2<\/sub>, NO, and NO2<\/sub>, as well as other air and water emissions.<\/p>\n

Economic considerations<\/h3>\n

Feedstock costs<\/h3>\n

Feedstock costs vary depending on their type and origin but, generally, agricultural residues have lower costs compared to energy crops. In Europe, for example, they range from \u20ac21 to \u20ac180pertonne (US$30\u2013250) of dry matter [12<\/a>]. Wood chips are at the upper end of the price range, whereas waste wood and agricultural residues are at the lower end; the average feedstock costs are below \u20ac60pertonne of dry matter. These costs do not include the transport costs to the biorefinery, which can be significant, depending on the moisture content and the distance travelled [13<\/a>].<\/p>\n

Capital costs<\/h3>\n

Because there are currently no commercial biorefinery installations, the capital costs of integrated biorefineries are uncertain, and most estimates are based on design data. For example, the capital costs of a biochemical refinery using corn stover as a feedstock are estimated at $232 million, and for the thermo-chemical at around $300 million [14<\/a>]. Integration into an existing refinery or chemical plant seems to be the most cost-effective option across the different processing routes; the integration can also accelerate the planning process and lower investment costs by around 25% [12<\/a>].<\/p>\n

Biofuel costs<\/h3>\n

Feedstock and capital costs affect the costs of biofuels and, to a certain extent, the costs of the co-products. Although costs of biofuels from integrated biorefineries are currently uncertain, it is clear that higher oil prices and energy security drivers are beginning to make them commercially more attractive and, as the \u2018economies of scale\u2019 increase (a saving in costs gained from higher production scales), it is expected that the costs of lignocellulosic fuels will be in the same range as biofuels from food crops. For example, in 2006 the costs of second-generation ethanol were estimated at $0.8\u20131.1perlitre, and these prices are expected to come down to $0.25\u20130.65perlitre by 2030 [10<\/a>]. This compares to a cost of $0.6\u20130.8perlitre in 2006 for ethanol from corn, rising to an estimated $0.35\u20130.55perlitre in 2030 [10<\/a>]. However, these costs do not take into account changes in land prices that may arise from competing demands from agriculture. The costs of other input materials in addition to feedstocks are not considered either, but they could also affect the biofuel prices. For example, the cost of enzymes is expected to reach $0.12\u20130.20perlitre of ethanol by 2015 [15<\/a>], representing 15\u201318% of current biofuel prices.<\/p>\n

Social considerations<\/h3>\n

Jobs and regional development<\/h3>\n

Cultivation of energy crops has the potential to create jobs in the agricultural sector. Although this potential is more limited for waste feedstocks, their use can provide an additional income to farmers and local communities, stimulating rural development. However, this could adversely affect farmers or a rural population that is dependent on residues for animal feed or domestic fuel [1<\/a>]. Further job opportunities exist during the construction and operation of biorefineries.<\/p>\n

Health issues<\/h3>\n

Human health can be affected in many different ways along the supply chain. For example, health hazards include emissions of particulates as a result of biomass handling and the toxicity of fertilizers and pesticides. The application of pesticides is estimated to cause 2 million cancer cases and 10000 deaths each year [1<\/a>].<\/p>\n

Human and labour rights<\/h3>\n

The issues of human and labour rights as well as gender discrimination are also relevant in this sector, especially in developing countries. Women are particularly vulnerable \u2013 they receive lower wages and are subjected to longer working hours than men [1<\/a>]. In some countries, child labour might also be an issue.<\/p>\n

Land availability and food prices<\/h3>\n

Energy crops could potentially compete with food crops for land, which could in turn affect food prices. For example, to meet the biofuel targets in Organisation for Economic Co-operation and Development (OECD) countries and some developing countries, accelerated production of lignocellulosic fuels could increase prices of cereal crops by around 15% by 2020. Using first-generation fuels would lead to a 30% price increase [9<\/a>].<\/p>\n

Intergenerational issues<\/h3>\n

Integrated biorefineries and their products have the potential to avoid or reduce the magnitude of some intergenerational issues associated with the use of fossil fuels. These include GHG emissions and related climate change impacts that would affect future generations. Similarly, avoiding the use of fossil fuels by using biofuels, biochemicals, and bioenergy helps save the fossil resources for future generations.<\/p>\n

Concluding remarks<\/h3>\n

The sustainability of integrated biorefineries and their products will depend on many technological, economic, environmental, and social factors. These will have to be evaluated carefully to ensure sustainable development of the sector.<\/p>\n

Arguably, however, the \u2018right\u2019 policies will have to be in place, promoting sustainable practices along the whole supply chain. For a more sustainable sector globally, concerted action is needed worldwide to ensure that the \u2018sustainability burden\u2019 is not shifted from developed to developing countries and that there is a fair sharing of costs and benefits along supply chains.<\/p>\n

References
\n<\/strong>1<\/a> Azapagic,\u00a0A., and Stichnothe,\u00a0H. (2011). Assessing sustainability of bio-fuels. In Sustainable Development in Practice: Case Studies for Engineers and Scientists. Azapagic,\u00a0A., Perdan,\u00a0S., eds. 2nd edn, (: John Wiley & Sons), pp.\u00a0142\u2013169. PubMed<\/a><\/em><\/p>\n

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2<\/a> Bringezu,\u00a0S., et\u00a0al. (2009). Towards Sustainable Production and Use of Resources: Assessing Bio-fuels. (: UNEP). PubMed<\/a><\/em><\/p>\n

3<\/a> Demirbas,\u00a0A. (2009). Biorefineries: current activities and future developments. Energy Convers. Manage. 50, 2782\u20132801. PubMed<\/a><\/em><\/p>\n

4<\/a> European Commission,\u00a0 (2009). In Directive 2009\/28\/EC of the European Parliament and of the Council of 23 April 2009 on the Promotion of the Use of Energy from Renewable Sources and Amending and Subsequently Repelling Directives 2001\/77\/EC and 2003\/30\/EC. European Commission. . PubMed<\/a><\/em><\/p>\n

5<\/a> US Federal Government,\u00a0 (2007). In Energy Independence and Security Act of 2007. Public Law 110\u2013140 \u2013 DEC. 19, 2007. US Federal Government. . PubMed<\/a><\/em><\/p>\n

6<\/a> US Department of Energy,\u00a0 (2013). Integrated Biorefineries: Bio-fuels, Biopower, and Bioproducts. (: Bioenergy Technologies Office, US Department of Energy). PubMed<\/a><\/em><\/p>\n

7<\/a> UK Department for Transport,\u00a0 (2008). Carbon and Sustainability Reporting Within the Renewable Transport Fuel Obligation\u2013Requirements and Guidance. (: UK Department for Transport). PubMed<\/a><\/em><\/p>\n

8<\/a> British Standards Institution,\u00a0 (2008). Publicly Available Specification PAS 2050:2008. Specification for the Assessment of the Life Cycle Greenhouse Gas Emissions of Goods and Services. (: British Standards Institution). PubMed<\/a><\/em><\/p>\n

9<\/a> Jeswani,\u00a0H.K., and Azapagic,\u00a0A. (2012). Life cycle sustainability assessment of second generation biodiesel. In Advances in Biodiesel Preparation \u2013 Second Generation Processes and Technologies. Luque,\u00a0R., Melero,\u00a0J.A., eds. (: Woodhead Publishers). PubMed<\/a><\/em><\/p>\n

10<\/a> The Royal Society,\u00a0 (2008). Sustainable Bio-fuels: Prospects and Challenges. (: The Royal Society). PubMed<\/a><\/em><\/p>\n

11<\/a> Gerbens-Leenesa,\u00a0W., et\u00a0al. (2009). Reply to Maes et al.: a global estimate of the water footprint of jatropha curcas under limited data availability. Proc. Natl. Acad. Sci. U.S.A. 106, E113. CrossRef<\/a> | PubMed<\/a><\/em><\/p>\n

12<\/a> Deutsche Erneuerbare Energieagentur,\u00a0 (2006). Biomass to Liquid \u2013 BTL Implementation Report (Executive Summary). (: Deutsche Erneuerbare Energieagentur). PubMed<\/a><\/em><\/p>\n

13<\/a> Azapagic,\u00a0A., et\u00a0al. (2011). Assessing biomass options for electricity generation on a life cycle basis. Waste Biomass Valor. 2, 33\u201343. PubMed<\/a><\/em><\/p>\n

14<\/a> US National Renewable Energy Laboratory,\u00a0 (2011). Process Design and Economics for Biochemical Conversion of Lignocellulosic Biomass to Ethanol: a) Dilute-Acid Pretreatment and Enzymatic Hydrolysis of Corn Stover. b) Thermochemical Pathway by Indirect Gasification and Mixed Alcohol Synthesis. (: US National Renewable Energy Laboratory). PubMed<\/a><\/em><\/p>\n

15<\/a> Mielenz,\u00a0J. (2001). Ethanol production from biomass: technology and commercialization status. Curr. Opin. Microbiol. 4, 324\u2013329. CrossRef<\/a> | PubMed<\/a><\/em><\/p>\n<\/div>\n","protected":false},"excerpt":{"rendered":"

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