Användare:StenS/Biobränsle utökning

Kolneutralitet (samordnas med avsnittet Klimatpåverkan

Ett biobränsleprojekt sägs vara koldioxidneutralt om den mängd CO ² som en växt har tagit upp under sin tillväxt kompenserar för de växthusgaser som frigörs vid förbränningen (CO ² är viktigast av växthusgaserna, och det finns 27% kol i CO ² ). ^[1] Detta omfattar även eventuella utsläpp som orsakas av en direkt eller indirekt förändring av markanvändningen. Många första generationens biobränsleprojekt är inte koldioxidneutrala utifrån på denna definition. Vissa projekt har ännu högre utsläpp än vissa fossilbaserade alternativ. ^[2] ^[3] ^[4]

Forts här: Det är den totala mängden absorption och utsläpp som tillsammans avgör om kostnaden för växthusgascykeln för ett biobränsleprojekt är positiv, neutral eller negativ. Om utsläppen under produktion, bearbetning, transport och förbränning är högre än vad som absorberas, både över och under marken under grödotillväxt, är växthusgasens livscykelkostnad positiv. På samma sätt, om den totala absorptionen är högre än de totala utsläppen, är livscykelkostnaden negativ. [[Kategori:Bränslen]] [[Kategori:Biobränslen]]

^ ”C vs CO2”. Energy Education. 2018-04-30. https://energyeducation.ca/encyclopedia/C_vs_CO2.
^ «The environmental costs and benefits of bioenergy have been the subject of significant debate, particularly for first‐generation biofuels produced from food (e.g. grain and oil seed). Studies have reported life‐cycle GHG savings ranging from an 86% reduction to a 93% increase in GHG emissions compared with fossil fuels (Searchinger et al., 2008; Davis et al., 2009; Liska et al., 2009; Whitaker et al., 2010). In addition, concerns have been raised that N2O emissions from biofuel feedstock cultivation could have been underestimated (Crutzen et al., 2008; Smith & Searchinger, 2012) and that expansion of feedstock cultivation on agricultural land might displace food production onto land with high carbon stocks or high conservation value (i.e. iLUC) creating a carbon debt which could take decades to repay (Fargione et al., 2008). Other studies have shown that direct nitrogen‐related emissions from annual crop feedstocks can be mitigated through optimized management practices (Davis et al., 2013) or that payback times are less significant than proposed (Mello et al., 2014). However, there are still significant concerns over the impacts of iLUC, despite policy developments aimed at reducing the risk of iLUC occurring (Ahlgren & Di Lucia, 2014; Del Grosso et al., 2014).» Whitaker, J., Field, J. L., Bernacchi, C. J., Cerri, C. E., Ceulemans, R., Davies, C. A., DeLucia, E. H., Donnison, I. S., McCalmont, J. P., Paustian, K., Rowe, R. L., Smith, P., Thornley, P. and McNamara, N. P. (2018), Consensus, uncertainties and challenges for perennial bioenergy crops and land use. GCB Bioenergy, 10: 150–164. https://doi.org/10.1111/gcbb.12488
^ «The impact of growing bioenergy and biofuel feedstock crops has been of particular concern, with some suggesting the greenhouse gas (GHG) balance of food crops used for ethanol and biodiesel may be no better or worse than fossil fuels (Fargione et al., 2008; Searchinger et al., 2008). This is controversial, as the allocation of GHG emissions to the management and the use of coproducts can have a large effect on the total carbon footprint of resulting bioenergy products (Whitaker et al., 2010; Davis et al., 2013). The potential consequences of land use change (LUC) to bioenergy on GHG balance through food crop displacement or 'indirect' land use change (iLUC) are also an important consideration (Searchinger et al., 2008).» Milner, S., Holland, R. A., Lovett, A., Sunnenberg, G., Hastings, A., Smith, P., Wang, S. and Taylor, G. (2016), Potential impacts on ecosystem services of land use transitions to second‐generation bioenergy crops in GB. GCB Bioenergy, 8: 317–333. https://doi.org/10.1111/gcbb.12263
^ «While the initial premise regarding bioenergy was that carbon recently captured from the atmosphere into plants would deliver an immediate reduction in GHG emission from fossil fuel use, the reality proved less straightforward. Studies suggested that GHG emission from energy crop production and land-use change might outweigh any CO2 mitigation (Searchinger et al., 2008; Lange, 2011). Nitrous oxide (N2O) production, with its powerful global warming potential (GWP), could be a significant factor in offsetting CO2 gains (Crutzen et al., 2008) as well as possible acidification and eutrophication of the surrounding environment (Kim & Dale, 2005). However, not all biomass feedstocks are equal, and most studies critical of bioenergy production are concerned with biofuels produced from annual food crops at high fertilizer cost, sometimes using land cleared from natural ecosystems or in direct competition with food production (Naik et al., 2010). Dedicated perennial energy crops, produced on existing, lower grade, agricultural land, offer a sustainable alternative with significant savings in greenhouse gas emissions and soil carbon sequestration when produced with appropriate management (Crutzen et al., 2008; Hastings et al., 2008, 2012; Cherubini et al., 2009; Don- dini et al., 2009a; Don et al., 2012; Zatta et al., 2014; Rich- ter et al., 2015).» McCalmont, J. P., Hastings, A., McNamara, N. P., Richter, G. M., Robson, P., Donnison, I. S. and Clifton‐Brown, J. (2017), Environmental costs and benefits of growing Miscanthus for bioenergy in the UK. GCB Bioenergy, 9, page 490. https://doi.org/10.1111/gcbb.12294

[Energy_Education_2018-1] ”C vs CO2”. Energy Education. 2018-04-30. https://energyeducation.ca/encyclopedia/C_vs_CO2.

[2] «The environmental costs and benefits of bioenergy have been the subject of significant debate, particularly for first‐generation biofuels produced from food (e.g. grain and oil seed). Studies have reported life‐cycle GHG savings ranging from an 86% reduction to a 93% increase in GHG emissions compared with fossil fuels (Searchinger et al., 2008; Davis et al., 2009; Liska et al., 2009; Whitaker et al., 2010). In addition, concerns have been raised that N2O emissions from biofuel feedstock cultivation could have been underestimated (Crutzen et al., 2008; Smith & Searchinger, 2012) and that expansion of feedstock cultivation on agricultural land might displace food production onto land with high carbon stocks or high conservation value (i.e. iLUC) creating a carbon debt which could take decades to repay (Fargione et al., 2008). Other studies have shown that direct nitrogen‐related emissions from annual crop feedstocks can be mitigated through optimized management practices (Davis et al., 2013) or that payback times are less significant than proposed (Mello et al., 2014). However, there are still significant concerns over the impacts of iLUC, despite policy developments aimed at reducing the risk of iLUC occurring (Ahlgren & Di Lucia, 2014; Del Grosso et al., 2014).» Whitaker, J., Field, J. L., Bernacchi, C. J., Cerri, C. E., Ceulemans, R., Davies, C. A., DeLucia, E. H., Donnison, I. S., McCalmont, J. P., Paustian, K., Rowe, R. L., Smith, P., Thornley, P. and McNamara, N. P. (2018), Consensus, uncertainties and challenges for perennial bioenergy crops and land use. GCB Bioenergy, 10: 150–164. https://doi.org/10.1111/gcbb.12488

[3] «The impact of growing bioenergy and biofuel feedstock crops has been of particular concern, with some suggesting the greenhouse gas (GHG) balance of food crops used for ethanol and biodiesel may be no better or worse than fossil fuels (Fargione et al., 2008; Searchinger et al., 2008). This is controversial, as the allocation of GHG emissions to the management and the use of coproducts can have a large effect on the total carbon footprint of resulting bioenergy products (Whitaker et al., 2010; Davis et al., 2013). The potential consequences of land use change (LUC) to bioenergy on GHG balance through food crop displacement or 'indirect' land use change (iLUC) are also an important consideration (Searchinger et al., 2008).» Milner, S., Holland, R. A., Lovett, A., Sunnenberg, G., Hastings, A., Smith, P., Wang, S. and Taylor, G. (2016), Potential impacts on ecosystem services of land use transitions to second‐generation bioenergy crops in GB. GCB Bioenergy, 8: 317–333. https://doi.org/10.1111/gcbb.12263

[4] «While the initial premise regarding bioenergy was that carbon recently captured from the atmosphere into plants would deliver an immediate reduction in GHG emission from fossil fuel use, the reality proved less straightforward. Studies suggested that GHG emission from energy crop production and land-use change might outweigh any CO2 mitigation (Searchinger et al., 2008; Lange, 2011). Nitrous oxide (N2O) production, with its powerful global warming potential (GWP), could be a significant factor in offsetting CO2 gains (Crutzen et al., 2008) as well as possible acidification and eutrophication of the surrounding environment (Kim & Dale, 2005). However, not all biomass feedstocks are equal, and most studies critical of bioenergy production are concerned with biofuels produced from annual food crops at high fertilizer cost, sometimes using land cleared from natural ecosystems or in direct competition with food production (Naik et al., 2010). Dedicated perennial energy crops, produced on existing, lower grade, agricultural land, offer a sustainable alternative with significant savings in greenhouse gas emissions and soil carbon sequestration when produced with appropriate management (Crutzen et al., 2008; Hastings et al., 2008, 2012; Cherubini et al., 2009; Don- dini et al., 2009a; Don et al., 2012; Zatta et al., 2014; Rich- ter et al., 2015).» McCalmont, J. P., Hastings, A., McNamara, N. P., Richter, G. M., Robson, P., Donnison, I. S. and Clifton‐Brown, J. (2017), Environmental costs and benefits of growing Miscanthus for bioenergy in the UK. GCB Bioenergy, 9, page 490. https://doi.org/10.1111/gcbb.12294

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