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A comparative cradle-to-gate life cycle assessment (LCA) including raw material acquisitions, rubber production and transportation of synthetic rubber (SBR) and two natural rubbers, namely imported Hevea and US-grown guayule, was conducted to quantify environmental impacts and to identify area(s) of environmental improvement. The use of co-products from the two natural rubbers as a source of energy was explored for their impacts and energy offset potential. Three environmental impact categories-ozone depletion (ODP), global warming (GWP), and acidification potential (AP)-and net energy were evaluated. Results indicated that guayule rubber had a lower ODP impact compared to SBR, and lower GWP and AP impacts compared to Hevea rubber. The Hevea rubber production with biodiesel co-product from seed oil scenario had the highest GWP and AP impacts, whereas guayule rubber production with bio-oil co-product from bagasse had the highest ODP impact. Only the scenario of Hevea rubber production with biodiesel production indicated an overall energy production of 3.25 MJ/kg rubber, whereas all other scenarios indicated a net energy consumption. However, co-products contributed to reduction in total energy consumed in every scenario that was investigated. The most promising guayule rubber scenario among the six examined was that with electricity production from bagasse, as it contributed the least to all three impact categories and yielded the most net energy. Sensitivity analysis on this most promising guayule scenario indicated rubber yield, water use and electricity for water pumping in guayule irrigation as the key parameters that have significant impacts on results. [ABSTRACT FROM AUTHOR]

Guayule ( Parthenium argentatum Gray) is an arid-adapted, low-input perennial shrub native to Mexico and southern Texas that has received considerable attention as an alternative source of natural rubber. It has potential to replace the most common types of rubbers, including synthetic rubber derived from petroleum and natural rubber, which is tapped from Hevea ( Hevea brasiliensis ) trees grown in tropical regions, primarily Southeast Asia. The guayule plant produces natural rubber in its bark parenchyma cells and the shrub is processed to extract the latex. Guayule rubber is comparable in quality to Hevea natural rubber and the residual, non-latex guayule plant material can be transformed into valuable co-products, such as bioenergy. This review introduces the reader to guayule rubber production (agriculture, processing and products) and explores the sustainability implications of guayule rubber commercialization related to the three pillars of sustainability, including environmental impacts of rubber production, economic barriers and advantages, and social implications. The review highlights areas of focus that could be leveraged to help guayule become a more sustainable source of natural rubber. Guayule rubber provides an opportunity to lower the environmental impacts of a major commodity, to develop an industry to support the local U.S, economy, and to reduce U.S. dependence on non-renewable petroleum sources and rubber imports. Proposed recommendations to further support guayule sustainability include improving the efficiency of agricultural and processing activities, utilization of guayule co-products to improve economics of guayule cultivation, and the establishment of a secure guayule rubber supply at a production level that could consistently meet rubber demands. A better understanding of guayule rubber life-cycle impacts could be a way to reduce the environmental footprint of guayule rubber products and expedite its commercialization. [ABSTRACT FROM AUTHOR]

Highlights: [•] This study investigated a cradle-to-gate microalgal biodiesel and its co-products. [•] Ozone depletion, global warming, smog, acidification and eutrophication potentials were assessed. [•] The market opportunities for each co-product were examined. [•] The scenario with the least life-cycle environmental impacts has the highest net energy ratio. [•] The scenario also had the highest total income indicating their co-products market potential. [ABSTRACT FROM AUTHOR]

Highlights: [•] Conducted a life cycle assessment (LCA) of microalgal diesel from PBR to combustion. [•] Compared the results with other existing LCA results of petroleum and other biodiesels. [•] Assessed the current Renewable Fuel Standard (RFS2). [•] Proposed an approach to set emission thresholds for eutrophication (EP) and smog formation potentials (PSP). [•] Future RFS should include a life-cycle emissions threshold for EP and PSP. [ABSTRACT FROM AUTHOR]

Abstract: A comparative life cycle assessment (LCA) was conducted on 20 scenarios of microalgae cultivation. These scenarios examined the utilization of nutrients and CO2 from synthetic sources and waste streams as well as the materials used to construct a photobioreactor (PBR). A 0.2-m3 closed PBR of Chlorella vulgaris at 30%-oil content by weight with the productivity of 25g/m2 ×day was used as a case study. Results of the study show that the utilization of resources from waste streams mainly avoided global warming potential (GWP) and eutrophication impacts. Impacts from the production of material used to construct the PBR dominate total impacts in acidification and ozone depletion categories, even over longer PBR lifetimes; thus, the choice of PBR construction materials is important. [Copyright &y& Elsevier]

Producing biofuel feedstock on marginal lands is a viable way to offset fossil fuel production, global warming, and other adverse environmental impacts, while at the same time performing positive ecosystem services by reclaiming unused areas with value producing activities. This research study explored low-input production of sunflower biodiesel feedstock on abandoned mine land (AML) from coal mining refuse treated with bauxite residue (alkaline clay) through the lens of Life Cycle Assessment (LCA). An attributional LCA was conducted from the gate of an aluminum production facility (which produces the bauxite residue), through AML amelioration and low-input agricultural activities, to the gate of a biodiesel production facility. A 26 ha (ha) coal mine refuse pile located in Mather, PA, (91 km south of Pittsburgh), was used as an example location. Analysis of published agricultural data and greenhouse research led to a conservative sunflower oilseed yield of 500 kg/ha estimate, with a subsequent biodiesel yield of 190 kg/ha (217 l/ha). Results show substantial impact from the initial soil amendment process, however, when compared to complete restoration of the AML and other similar fuel production activities, overall environmental impacts over a twenty-year production cycle are sensible. An alternative allocation of the bauxite residue transport (i.e. associating transport impacts to aluminum industry) and addition of other fuel conversion pathways would show an improved energy return and better environmental outlook from biofuel production on AML. [ABSTRACT FROM AUTHOR]