An effective surfactant-assisted hydrothermal pretreatment strategy for bioethanol production from chili post-harvest residue by separate hydrolysis and fermentation

Bioprocess and Biosystems Engineering - Surfactants play major role in the delignification of lignocellulosic biomass. Surfactant-assisted hydrothermal pretreatment was evaluated for chili...     

Refining sweet sorghum to ethanol and sugar: economic trade-offs in the context of North China

Reducing the use of non-renewable fossil energy reserves together with improving the environment are two important reasons that drive interest in the use of bioethanol as an automotive fuel. Conversion of sugar and starch to ethanol has been proven at an industrial scale in Brazil and the United States, respectively, and this alcohol has been able to compete with conventional gasoline due to various incentives. In this paper, we examined making ethanol from the sugar extracted from the juice of sweet sorghum and/or from the hemicellulose and cellulose in the residual sorghum bagasse versus selling the sugar from the juice or burning the bagasse to make electricity in four scenarios in the context of North China. In general terms, the production of ethanol from the hemicellulose and cellulose in bagasse was more favorable than burning it to make power, but the relative merits of making ethanol or sugar from the juice was very sensitive to the price of sugar in China. This result was confirmed by both process economics and analysis of opportunity costs. Thus, a flexible plant capable of making both sugar and fuel-ethanol from the juice is recommended. Overall, ethanol production from sorghum bagasse appears very favorable, but other agricultural residues such as corn stover and rice hulls would likely provide a more attractive feedstock for making ethanol in the medium and long term due to their extensive availability in North China and their independence from other markets. Furthermore, the process for residue conversion was based on particular design assumptions, and other technologies could enhance competitiveness while considerations such as perceived risk could impede applications.     

Life cycle assessment of soybean-based biodiesel in Argentina for export

Background, aim and scope

Regional specificities are a key factor when analyzing the environmental impact of a biofuel pathway through a life cycle assessment (LCA). Due to different energy mixes, transport distances, agricultural practices and land use changes, results can significantly vary from one country to another. The Republic of Argentina is the first exporter of soybean oil and meal and the third largest soybean producer in the world, and therefore, soybean-based biodiesel production is expected to significantly increase in the near future, mostly for exportation. Moreover, Argentinean biodiesel producers will need to evaluate the environmental performances of their product in order to comply with sustainability criteria being developed. However, because of regional specificities, the environmental performances of this biofuel pathway can be expected to be different from those obtained for other countries and feedstocks previously studied. This work aims at analyzing the environmental impact of soybean-based biodiesel production in Argentina for export. The relevant impact categories account for the primary non-renewable energy consumption (CED), the global warming potential (GWP), the eutrophication potential (EP), the acidification potential (AP), the terrestrial ecotoxicity (TE), the aquatic ecotoxicity (AE), the human toxicity (HT) and land use competition (LU). The paper tackles the feedstock and country specificities in biodiesel production by comparing the results of soybean-based biodiesel in Argentina with other reference cases. Emphasis is put on explaining the factors that contribute most to the final results and the regional specificities that lead to different results for each biodiesel pathway.

Materials and methods

The Argentinean (AR) biodiesel pathway was modelled through an LCA and was compared with reference cases available in the ecoinvent® 2.01 database, namely, soybean-based biodiesel production in Brazil (BR) and the United States (US), rapeseed-based biodiesel production in the European Union (EU) and Switzerland (CH) and palm-oil-based biodiesel production in Malaysia (MY). In all cases, the systems were modelled from feedstock production to biodiesel use as B100 in a 28 t truck in CH. Furthermore, biodiesel pathways were compared with fossil low-sulphur diesel produced and used in CH. The LCA was performed according to the ISO standards. The life cycle inventory and the life cycle impact assessment (LCIA) were performed in Excel spreadsheets using the ecoinvent® 2.01 database. The cumulative energy demand (CED) and the GWP were estimated through the CED for fossil and nuclear energy and the IPCC 2001 (climate change) LCIA methods, respectively. Other impact categories were assessed according to CML 2001, as implemented in ecoinvent. As the product is a fuel for transportation (service), the system was defined for one vehicle kilometre (functional unit) and was divided into seven unit processes, namely, agricultural phase, soybean oil extraction and refining, transesterification, transport to port, transport to the destination country border, distribution and utilisation.

Results

The Argentinean pathway results in the highest GWP, CED, AE and HT compared with the reference biofuel pathways. Compared with the fossil reference, all impact categories are higher for the AR case, except for the CED. The most significant factor that contributes to the environmental impact in the Argentinean case varies depending on the evaluated category. Land provision through deforestation for soybean cultivation is the most impacting factor of the AR biodiesel pathway for the GWP, the CED and the HT categories. Whilst nitrogen oxide emissions during the fuel use are the main cause of acidification, nitrate leaching during soybean cultivation is the main factor of eutrophication. LU is almost totally affected by arable land occupation for soybean cultivation. Cypermethrin used as pesticide in feedstock production accounts for almost the total impact on TE and AE.

Discussion

The sensitivity analysis shows that an increase of 10% in the soybean yield, whilst keeping the same inputs, will reduce the total impact of the system. Avoiding deforestation is the main challenge to improve the environmental performances of soybean-based biodiesel production in AR. If the soybean expansion can be done on marginal and set-aside agricultural land, the negative impact of the system will be significantly reduced. Further implementation of crops’ successions, soybean inoculation, reduced tillage and less toxic pesticides will also improve the environmental performances. Using ethanol as alcohol in the transesterification process could significantly improve the energy balance of the Argentinean pathway.

Conclusions

The main explaining factors depend on regional specificities of the system that lead to different results from those obtained in the reference cases. Significantly different results can be obtained depending on the level of detail of the input data, the use of punctual or average data and the assumptions made to build up the LCA inventory. Further improvement of the AR biodiesel pathways should be done in order to comply with international sustainability criteria on biofuel production.

Recommendations and perspectives

Due to the influence of land use changes in the final results, more efforts should be made to account for land use changes others than deforestation. More data are needed to determine the part of deforestation attributable to soybean cultivation. More efforts should be done to improve modelling of interaction between variables and previous crops in the agricultural phase, future transesterification technologies and market prices evolution. In order to assess more accurately the environmental impact of soybean-based biodiesel production in Argentina, further considerations should be made to account for indirect land use changes, domestic biodiesel consumption and exportation to other regions, production scale and regional georeferenced differentiation of production systems.     

Recent advances in microbial production of malic acid from renewable byproducts

In the last few years, ecofriendly malic acid production has received a potential platform for the bio-based chemicals to replace the dependency of fossil based resources. The main goal of this paper is to explore the feasibility of efficient production of malic acid from cost effective alternative renewable byproducts as feedstock. To replace the traditional method of malic acid production from petroleum-based compounds such as maleic acid, the efficiency of fermentation technology for malic acid production using various microorganisms has been improved. To date, glucose is designated as the best substrate for malic acid production. However, few reviews concerning about malic acid production by employing various microbial strains were reported. The current knowledge on the biosynthesis of malic acid has assisted to improve malic acid production using various microbial strains. But, there is still need for the continuous production and replacement of low-cost substrates to increase the yield of malic acid. This review provides an overview about progress, achievements, merits, challenges and future perspectives in malic acid production from cost effective alternative substrates. Thus, malic acid production can be economical using renewable byproducts like crude glycerol by employing appropriate microorganism.

     

Protein extraction from biomass in a bioethanol refinery - Possible dietary applications: Use as animal feed and potential extension to human consumption

The economy of the production of lignocellulosic ethanol could be supported by the simultaneous use of different components of the biomass other than sugars. Among these, protein is present at high concentration in leaves and is a candidate for different possible utilizations. Among dietary applications, plant protein may be used as animal feed and possibly extended to human consumption, in close similarity to leaf protein concentrates already proposed in the past. This would be especially beneficial for developing countries. For this aim, protein quality plays a crucial role: separating only the noble fraction of protein in biomass and preserving its nutritional value, while simultaneously obtaining good yields and limiting drawbacks on other steps of the production chain is particularly challenging from a technical viewpoint. In this review, we compare the possible extraction of protein from dry biomass with the more commonly studied situation in which freshly harvested material is used, with special focus on dietary implications.     

Life cycle assessment of biofuels: Energy and greenhouse gas balances

The promotion of biofuels as energy for transportation in the industrialized countries is mainly driven by the perspective of oil depletion, the concerns about energy security and global warming. However due to sustainability constraints, biofuels will replace only 10 to 15% of fossil liquid fuels in the transport sector. Several governments have defined a minimum target of GHG emissions reduction for those biofuels that will be eligible to public incentives, for example a 35% emissions reduction in case of biofuels in Members States of the European Union. This article points out the significant biases in estimating GHG balances of biofuels stemming from modelling choices about system definition and boundaries, functional unit, reference systems and allocation methods. The extent to which these choices influence the results is investigated. After performing a comparison and constructive criticism of various modelling choices, the LCA of wheat-to-bioethanol is used as an illustrative case where bioethanol is blended with gasoline at various percentages (E5, E10 and E85). The performance of these substitution options is evaluated as well. The results show a large difference in the reduction of the GHG emissions with a high sensitivity to the following factors: the method used to allocate the impacts between the co-products, the type of reference systems, the choice of the functional unit and the type of blend. The authors come out with some recommendations for basing the estimation of energy and GHG balances of biofuels on principles such as transparency, consistency and accuracy.     

Induction of Plasmodium falciparum-specific CD4+ T cells and memory B cells in Gabonese children vaccinated with RTS,S/AS01(E) and RTS,S/AS02(D)

The recombinant circumsporozoite protein (CS) based vaccine, RTS,S, confers protection against Plasmodium falciparum infection in controlled challenge trials and in field studies. The RTS,S recombinant antigen has been formulated with two adjuvant systems, AS01 and AS02, which have both been shown to induce strong specific antibody responses and CD4 T cell responses in adults. As infants and young children are particularly susceptible to malaria infection and constitute the main target population for a malaria vaccine, we have evaluated the induction of adaptive immune responses in young children living in malaria endemic regions following vaccination with RTS,S/AS01(E) and RTS,S/AS02(D). Our data show that a CS-specific memory B cell response is induced one month after the second and third vaccine dose and that CS-specific antibodies and memory B cells persist up to 12 months after the last vaccine injection. Both formulations also induced low but significant amounts of CS-specific IL-2(+) CD4(+) T cells one month after the second and third vaccine dose, upon short-term in vitro stimulation of whole blood cells with peptides covering the entire CS derived sequence in RTS,S. These results provide evidence that both RTS,S/AS01(E) and RTS,S/AS02(D) induced adaptive immune responses including antibodies, circulating memory B cells and CD4(+) T cells directed against P. falciparum CS protein. TRIAL REGISTRATION: ClinicalTrials.gov NCT00307021.     

Cyanobacteria and microalgae: a positive prospect for biofuels

Biofuel-bioenergy production has generated intensive interest due to increased concern regarding limited petroleum-based fuel supplies and their contribution to atmospheric CO2 levels. Biofuel research is not just a matter of finding the right type of biomass and converting it to fuel, but it must also be economically sustainable on large-scale. Several aspects of cyanobacteria and microalgae such as oxygenic photosynthesis, high per-acre productivity, non-food based feedstock, growth on non-productive and non-arable land, utilization of wide variety of water sources (fresh, brackish, seawater and wastewater) and production of valuable co-products along with biofuels have combined to capture the interest of researchers and entrepreneurs. Currently, worldwide biofuels mainly in focus include biohydrogen, bioethanol, biodiesel and biogas. This review focuses on cultivation and harvesting of cyanobacteria and microalgae, possible biofuels and co-products, challenges for cyanobacterial and microalgal biofuels and the approaches of genetic engineering and modifications to increase biofuel production.