Comparative analysis for power generation and ethanol production from sugarcane residual biomass in Brazil

This work compares the technical, economic and environmental (GHG emissions mitigation) performance of power generation and ethanol production from sugarcane residual biomass, considering conversion plants adjacent to a sugarcane mill in Brazil. Systems performances were simulated for a projected enzymatic saccharification co-fermentation plant (Ethanol option) and for a commercial steam-Rankine power plant (Electricity option). Surplus bagasse from the mill would be used as fuel/raw material for conversion, while cane trash collected from the field would be used as supplementary fuel at the mill. For the Electricity option, the sugarcane biorefinery (mill+adjacent plant) would produce 91 L of ethanol per tonne of cane and export 130 kWh/t of cane, while for the Ethanol option the total ethanol production would be 124 L/t of cane with an electricity surplus of 50 kWh/t cane. The return on investment (ROI) related to the biochemical conversion route was 15.9%, compared with 23.2% for the power plant, for the conditions in Brazil. Considering the GHG emissions mitigation, the environmentally preferred option is the biochemical conversion route: the net avoided emissions associated to the adjacent plants are estimated to be 493 and 781 kgCO2eq/t of dry bagasse for the Electricity and Ethanol options, respectively.Cellulosic ethanol Bioelectricity CHP

Mitigating carbon emissions through sustainable aviation fuels: costs and potential

In general, the certified pathways for the production of sustainable aviation fuels (SAFs) are still far from being competitive with fossil kerosene, although they have the potential to reduce greenhouse gas (GHG) emissions. However, the mitigation costs related to SAFs and how they compete with the carbon credits market remain unclear. The present study addressed these issues, evaluating SAF pathways based on hydrotreatment (HEFA process) of soybean oil, palm oil, used cooking oil (UCO) and beef tallow; dehydration and oligomerization of ethanol (ATJ technology) obtained from sugarcane, lignocellulosic residues, and steel off-gases; and the thermochemical conversion of lignocellulosic residues using the Fischer–Tropsch (FT) process and hydrothermal liquefaction (HTL). Residue-based pathways had lower mitigation costs. Used cooking oil / HEFA had the lowest value (185 USD tCO2e−1), followed by the thermochemical conversion of forestry residues (234–263 USD tCO2e−1). Of the 1G pathways, SAF production from 1G sugarcane ethanol (SC-1G/ATJ) performed better (495 USD tCO2e−1) than oil-based ones. In comparison with the carbon market, the mitigation costs of SAFs are much higher than the current prices or even future ones. However, several concerns about the credibility of the emission units and their effective mitigation effects indicate that SAFs could play an important role in aviation sector goals. Considering the potential of supplying SAF and mitigating emissions, SC-1G/ATJ was suggested as a preferred alternative in the short term. Of the residue-based pathways, tallow / HEFA and FT of forestry residues are suggested as strategic alternatives.</p

The carbon footprint of alternative jet fuels produced in Brazil: exploring different approaches

Although the potential of Alternative Jet Fuels (AJF) to reduce greenhouse gases (GHG) emissions has been widely reported upon in the literature, there are still discrepancies among the results. These may be due to the different GHG accounting methods, including those used by different Low-Carbon Policies (LCPs). To have a clearer understanding of the life cycle performance of AJF, the carbon footprint of ten pathways was estimated, comprising promising feedstocks – such as soybean, palm, sugarcane, sugarcane residues, forestry residues, used cooking oil, beef tallow, and steel off-gases – and ASTM-approved technologies: Hydroprocessed Fatty Acids, Alcohol-to-Jet, and Fischer-Tropsch. Six methodological approaches were used: the attributional and the consequential life cycle assessment, as well as guidelines for the four LCPs: Renovabio (Brazil), CORSIA (aviation sector), RFS (United States), and RED II (Europe). Soybean-based pathway (24 to 98.7 gCO2e/MJ) had the low to no potential for reducing GHG when compared to their fossil counterparts, mainly due to land use change. Of all food-based pathways, AJF produced from sugarcane performed the best (-10.4 to 43.7 gCO2e/MJ), especially when power surplus was credited. AJF from palm oil could present significant GHG reduction for palm expansion in degraded pasturelands. By contrast, Fischer-Tropsch of lignocellulosic residues showed the highest potential for reducing GHG (-95% to -130%). Different from food-based pathways, the potential GHG reduction of residues-based pathways converged within a narrower range (-130% to -50%), except when residual feedstocks have to be redirected from their current economic use. It could lead to GHG emissions higher than fossil fuel.BT/Biotechnology and Societ

Mitigating carbon emissions through sustainable aviation fuels: costs and potential

In general, the certified pathways for the production of sustainable aviation fuels (SAFs) are still far from being competitive with fossil kerosene, although they have the potential to reduce greenhouse gas (GHG) emissions. However, the mitigation costs related to SAFs and how they compete with the carbon credits market remain unclear. The present study addressed these issues, evaluating SAF pathways based on hydrotreatment (HEFA process) of soybean oil, palm oil, used cooking oil (UCO) and beef tallow; dehydration and oligomerization of ethanol (ATJ technology) obtained from sugarcane, lignocellulosic residues, and steel off-gases; and the thermochemical conversion of lignocellulosic residues using the Fischer–Tropsch (FT) process and hydrothermal liquefaction (HTL). Residue-based pathways had lower mitigation costs. Used cooking oil / HEFA had the lowest value (185 USD tCO2e−1), followed by the thermochemical conversion of forestry residues (234–263 USD tCO2e−1). Of the 1G pathways, SAF production from 1G sugarcane ethanol (SC-1G/ATJ) performed better (495 USD tCO2e−1) than oil-based ones. In comparison with the carbon market, the mitigation costs of SAFs are much higher than the current prices or even future ones. However, several concerns about the credibility of the emission units and their effective mitigation effects indicate that SAFs could play an important role in aviation sector goals. Considering the potential of supplying SAF and mitigating emissions, SC-1G/ATJ was suggested as a preferred alternative in the short term. Of the residue-based pathways, tallow / HEFA and FT of forestry residues are suggested as strategic alternatives.BT/Biotechnology and Societ

Environmental trade-offs of renewable jet fuels in Brazil: Beyond the carbon footprint

The use of renewable jet fuels (RJFs) is an option for meeting the greenhouse gases (GHG) reduction targets of the aviation sector. Therefore, most of the studies have focused on climate change indicators, but other environmental impacts have been disregarded. In this paper, an attributional life cycle assessment is performed for ten RJF pathways in Brazil, considering the environmental trade-offs between climate change and seven other categories, i.e., fossil depletion, terrestrial acidification, eutrophication, human and environmental toxicity, and air quality-related categories, such as particulate matter and photochemical oxidant formation. The scope includes sugarcane and soybean for first-generation (1G) pathways and residual materials (wood and sugarcane residues, beef tallow, and used cooking oil-UCO) for second-generation (2G) pathways. Three certified technologies to produce RJF are considered: hydroprocessed esters and fatty acids (HEFA), alcohol-to-jet (ATJ), and Fischer-Tropsch (FT). Assuming the residual feedstocks as wastes or by-products, the 2G pathways are evaluated by two different approaches, in which the biomass sourcing processes are either accounted for or not. Results show that 1G pathways lead to significant GHG reductions compared to fossil kerosene from 55% (soybean/HEFA) to 65% (sugarcane/ATJ). However, the sugarcane-based pathway generated three-fold higher values than fossil kerosene for terrestrial acidification and air quality impacts, and seven-fold for eutrophication. In turn, soybean/HEFA caused five-fold higher levels of human toxicity. For 2G pathways, when the residual feedstock is assumed to be waste, the potential GHG emission reduction is over 74% with no relevant trade-offs. On the other hand, if the residual feedstocks are assumed as valuable by-products, tallow/HEFA becomes the worst option and pathways from sugarcane residues, even providing a GHG reduction of 67% to 94%, are related to higher impacts than soybean/HEFA for terrestrial acidification and air quality. FT pathways represent the lowest impacts for all categories within both approaches, followed by UCO/HEFA.BT/Biotechnology and SocietyBT/Bioprocess Engineerin