Recent Advances in the Biosynthesis of Polyhydroxyalkanoates from Lignocellulosic Feedstocks

Polyhydroxyalkanoates (PHA) are biodegradable polymers that are considered able to replace synthetic plastic because their biochemical characteristics are in some cases the same as other biodegradable polymers. However, due to the disadvantages of costly and non-renewable carbon sources, the production of PHA has been lower in the industrial sector against conventional plastics. At the same time, first-generation sugar-based cultivated feedstocks as substrates for PHA production threatens food security and considerably require other resources such as land and energy. Therefore, attempts have been made in pursuit of suitable sustainable and affordable sources of carbon to reduce production costs. Thus, in this review, we highlight utilising waste lignocellulosic feedstocks (LF) as a renewable and inexpensive carbon source to produce PHA. These waste feedstocks, second-generation plant lignocellulosic biomass, such as maize stoves, dedicated energy crops, rice straws, wood chips, are commonly available renewable biomass sources with a steady supply of about 150 billion tonnes per year of global yield. The generation of PHA from lignocellulose is still in its infancy, hence more screening of lignocellulosic materials and improvements in downstream processing and substrate pre-treatment are needed in the future to further advance the biopolymer sector.

Cellulosic biofuel production using emulsified simultaneous saccharification and fermentation (eSSF) with conventional and thermotolerant yeasts

Background Future expansion of corn-derived ethanol raises concerns of sustainability and competition with the food industry. Therefore, cellulosic biofuels derived from agricultural waste and dedicated energy crops are necessary. To date, slow and incomplete saccharification as well as high enzyme costs have hindered the economic viability of cellulosic biofuels, and while approaches like simultaneous saccharification and fermentation (SSF) and the use of thermotolerant microorganisms can enhance production, further improvements are needed. Cellulosic emulsions have been shown to enhance saccharification by increasing enzyme contact with cellulose fibers. In this study, we use these emulsions to develop an emulsified SSF (eSSF) process for rapid and efficient cellulosic biofuel production and make a direct three-way comparison of ethanol production between S. cerevisiae, O. polymorpha, and K. marxianus in glucose and cellulosic media at different temperatures. Results In this work, we show that cellulosic emulsions hydrolyze rapidly at temperatures tolerable to yeast, reaching up to 40-fold higher conversion in the first hour compared to microcrystalline cellulose (MCC). To evaluate suitable conditions for the eSSF process, we explored the upper temperature limits for the thermotolerant yeasts Kluyveromyces marxianus and Ogataea polymorpha, as well as Saccharomyces cerevisiae, and observed robust fermentation at up to 46, 50, and 42 °C for each yeast, respectively. We show that the eSSF process reaches high ethanol titers in short processing times, and produces close to theoretical yields at temperatures as low as 30 °C. Finally, we demonstrate the transferability of the eSSF technology to other products by producing the advanced biofuel isobutanol in a light-controlled eSSF using optogenetic regulators, resulting in up to fourfold higher titers relative to MCC SSF. Conclusions The eSSF process addresses the main challenges of cellulosic biofuel production by increasing saccharification rate at temperatures tolerable to yeast. The rapid hydrolysis of these emulsions at low temperatures permits fermentation using non-thermotolerant yeasts, short processing times, low enzyme loads, and makes it possible to extend the process to chemicals other than ethanol, such as isobutanol. This transferability establishes the eSSF process as a platform for the sustainable production of biofuels and chemicals as a whole.

Consumer Preferences and Willingness to Pay for Potting Mix with Biochar

Biochar is a co-product of advanced biofuels production from feedstocks including food, agricultural, wood wastes, or dedicated energy crops. Markets for soil amendments using biochar are emerging, but little is known about consumer preferences and willingness to pay (WTP) for these products or the depth of the products’ market potential for this product. This research provides WTP estimates for potting mix amended with 25% biochar, conditioned on consumer demographics and attitudes about product information labeling. Data were collected with an online survey of 577 Tennessee home gardeners. WTP was elicited through a referendum contingent valuation. Consumer WTP for an 8.81 L bag of 25% biochar potting mix is $8.52; a premium of $3.53 over conventional potting mix. Demographics and attitudes toward biofuels and the environment influence WTP. Biochar amounts demanded are projected for the study area’s potential market. Optimal prices, profits, and market shares are estimated across different marginal costs of producing biochar potting mix.

Assessment of Tomato Peels Suitable for Producing Biomethane within the Context of Circular Economy: A GIS-Based Model Analysis

Biomass is seen as one of the most dominant future renewable energy sources. In detail, agro-industrial by-products represent a cheap, renewable, and abundant feedstock useful for several new products, including biochemical, biomaterials, and above all biogas, which are taking on an ever-increasing role in Italy. In this context, the tomato chain was analysed aiming at estimating the amount of processed tomato and the related waste production as a new suitable resource for producing biofuel as a new frontier within the context of a circular economy. Due the importance of the tomato industry, this research aims at filling gaps in the knowledge of the production and yield of the by-products that are useful as biomass for energy use in those territorial areas where the biomethane sector is still developing. This aim could be relevant for planning the sustainable development of the biomethane sector by reducing both soil consumption for dedicated energy crops and GHG emissions coming from the biomass logistic supply. The achieved results show the localization of territorial areas highly characterized by this kind of biomass. Therefore, it would be desirable that the future policies of development in the biomethane sector consider the availability and the distribution of these suitable biomasses within the territory.

Torrefaction Temperature and Holding Time Effect on Khaya Senegalensis Biomass

Khaya senegalensis is fast growing plant, can be planted in marginal land and grow easily in Malaysia. Therefore, it has the potential to be developed as dedicated energy crops. This study was conducted to determine the effect of torrefaction in upgrading the quality of Khaya senegalensis biomass. Torrefaction has been known as one of the most promising pre-treatments for biomass. In this experiment, the biomass sample was torrefied in the muffle furnace at four different temperatures (225, 250, 275 and 300°C) and three durations (30, 60 and 90 minutes). The results show that both torrefaction temperature and duration posed strong impact on the biomass quality. It was found that the volatile matters of the biomass reduce significantly as the torrefaction severity increase. On the other hand, the ash and carbon content increase with the increasing temperature and duration. Most importantly the calorific value of the biomass sample amplifies to 22.26Mj/kg from 16.11Mj/kg of untreated sample when torrefied at 300°C for 90 minutes.