Tobacco waste valorization through composting: A systematic review of biomass conversion efficiency and circular bioeconomy strategies

Quantifying actual and theoretical ethanol yields from biomass conversion processes such as simultanteous saccharification and fermentation (SSF) requires expensive, complex fermentation assays, and extensive compositional analyses of the biomass sample. Near-infrared reflectance spectroscopy (NIRS) is a non-destructive technology that can be used to obtain rapid, low-cost, high-throughput, and accurate estimates of agricultural product composition. In this study, broad-based NIRS calibrations were developed for switchgrass biomass that can be used to estimate over 20 components including cell wall and soluble sugars and also ethanol production and pentose sugars released as measured using a laboratory SSF procedure. With this information, an additional 13 complex feedstock traits can be determined including theoretical and actual ethanol yields from hexose fermentation. The NIRS calibrations were used to estimate feedstock composition and conversion information for biomass samples from a multi-year switchgrass (Panicum virgatum L.) biomass cultivar evaluation trial. There were significant differences among switchgrass strains for all biomass conversion and composition traits including actual ethanol yields, ETOHL (L Mg−1) and theoretical ethanol yields, ETOHTL (L Mg−1), based on cell wall and non-cell wall composition NIRS analyses. ETOHL means ranged from 98 to 115 L Mg−1 while ETOHTL means ranged from 203 to 222 L Mg−1. Because of differences in both biomass yields and conversion efficiency, there were significant differences among strains for both actual (2,534–3,720 L ha−1) and theoretical (4,878–7,888 L ha−1) ethanol production per hectare. It should be feasible to improve ethanol yields per hectare by improving both biomass yield and conversion efficiency by using NIRS analyses to quantify differences among cultivars and management practices.

Conversion of cellulosic biomass towards added value products over bifunctional

As national governments continue developing bioeconomy strategies, the forest-based sector becomes increasingly important. Romania’s forest sector can be at the heart of a sustainable circular-bioeconomy transition. However, despite recently launching its national forest strategy, the country has yet to produce a comprehensive bioeconomy strategy where the forest sector is properly acknowledged and integrated. Here, we discuss the potential opportunities and challenges for developing a national circular–bioeconomy strategy that builds around the forest-based sector. Methodologically, we build on qualitative insights from two foresight workshops conducted with 16 international experts. Conceptually, we draw on recent forest-based circular-bioeconomy literature, which we synthesize and use to complement the insights provided by workshop participants. Three main key findings emerged from this analysis: (i) Several knowledge gaps related to biomass availability, carbon storage, biodiversity status, ecosystem services, or governance arrangements persist. (ii) A circular forest bioeconomy must focus on regional and rural development, including both traditional wood use, as well as new wood-based products. Finally, (iii) the transition to a forest-based bioeconomy requires substantial investments in areas such as forest infrastructure, education, and labor force. Forward-looking policies can address these challenges by fostering new ways of thinking, collaborating and researching the bioeconomy. We anticipate our article to be a starting point for more informed discussions around the role of forests and the forest-based sector in Romania’s future bioeconomy strategy. Furthermore, as work around the implementation of the national forest strategy has recently commenced, the ideas discussed here could help decision-makers better integrate and coordinate national and European forest policies with bioeconomy ambitions.

Circumstantial factors and local collaboration determine farmers' perceptions and practices on circular bioeconomy – examples from Southern Sweden

For lignocellulosic bioenergy to be economically viable, genetic improvements must be made in feedstock quality including both biomass total yield and conversion efficiency. Toward this goal, multiple studies have considered candidate genes and discovered quantitative trait loci (QTL) associated with total biomass accumulation and/or grain production in bioenergy grass species including maize and sorghum. However, very little research has been focused on genes associated with increased biomass conversion efficiency. In this study, Trichoderma viride fungal cellulase hydrolysis activity was measured for lignocellulosic biomass (leaf and stem tissue) obtained from individuals in a F5 recombinant inbred Sorghum bicolor×Sorghum propinquum mapping population. A total of 49 QTLs (20 leaf, 29 stem) were associated with enzymatic conversion efficiency. Interestingly, six high-density QTL regions were identified in which four or more QTLs overlapped. In addition to enzymatic conversion efficiency QTLs, two QTLs were identified for biomass crystallinity index, a trait which has been shown to be inversely correlated with conversion efficiency in bioenergy grasses. The identification of these QTLs provides an important step toward identifying specific genes relevant to increasing conversion efficiency of bioenergy feedstocks. DNA markers linked to these QTLs could be useful in marker-assisted breeding programs aimed at increasing overall bioenergy yields concomitant with selection of high total biomass genotypes.

Sugarcane is a lignocellulosic crop which is used to produce sugar in sugarcane processing industries. Globally, sugarcane processing industries generate solid and liquid wastes amounting to more than 279 million tons per annum and by-products; namely, trash, bagasse, mill mud, and molasses. The valorisation of waste and by-products has recently increased and is playing a significant role in achieving policies and goals associated with circular bioeconomy and sustainable development. For the valorisation of sugarcane processing industry waste and by-products, a number of technologies are well established and in use, while other innovative technologies are still ongoing through research and development with promising futures. These by-products obtained from sugarcane processing industries can be converted into biofuels like hydrogen and methane via anaerobic digestion. Molasses belongs to the first-generation (1G) waste, while trash, bagasse, and mill mud belong to second-generation (2G) waste. Various studies have been carried out in converting both first- and second-generation sugarcane processing industry wastes into renewable energy, exploiting anaerobic digestion (AD) and dark fermentation (DF). This review emphasises the various factors affecting the AD and DF of 1G and 2G sugarcane processing industry wastes. It also critically addresses the feasibility and challenges of operating a two-stage anaerobic digestion process for hydrogen and methane production from these wastes.

Circular bioeconomy of coffee industries: Energy and techno-economic approach based on biogas and biomethane production

Using a wide range of organic substrates in the methane fermentation process enables efficient biogas production. Nonetheless, in many cases, the efficiency of electricity generation in biogas plant cogeneration systems is much lower than expected, close to the calorific value of the applied feedstock. This paper analyses the energy conversion efficiency in a 1 MWel agricultural biogas plant fed with corn silage or vegetable waste and pig slurry as a feedstock dilution agent, depending on the season and availability. Biomass conversion studies were carried out for 12 months, during which substrate samples were taken once a month. The total primary energy in the substrates was estimated in laboratory conditions by measuring the released heat (17,760 MWh·year−1), and, in the case of pig slurry, biochemical methane potential (BMP, (201.88 ± 3.21 m3·Mg VS−1). Further, the substrates were analysed in terms of their chemical composition, from protein, sugar and fat content to mineral matter determination, among other things. The results obtained during the study were averaged. Based on such things as the volume of the biogas, the amount of chemical (secondary) energy contained in methane as a product of biomass conversion (10,633 MWh·year−1) was calculated. Considering the results obtained from the analyses, as well as the calculated values of the relevant parameters, the biomass conversion efficiency was determined as the ratio of the chemical energy in methane to the (primary) energy in the substrates, which was 59.87%, as well as the electricity production efficiency, as the ratio of the electricity produced (4913 MWh·year−1) to the primary energy, with a 35% cogeneration system efficiency. The full energy conversion efficiency, related to electricity production, reached a low value of 27.66%. This article provides an insightful, unique analysis of energy conversion in an active biogas plant as an open thermodynamic system.

The 2018 European bioeconomy strategy sets a new vision for Europe's sustainable development: a transition to regenerative resource usage that embraces circular principles. Similarly, various member states have developed national bioeconomy strategies. To be effective, such strategies require methodologically sound monitoring tools that support the alignment of national and urban policies. Indeed, cities are central to the bioeconomy, mobilizing ever increasing amounts of biogenic materials. To better understand the suitability of national bioeconomy strategies for guiding urban circular bioeconomy transitions, this paper examines the composition, features, and topical coverage of national bioeconomy indicator sets with a threefold analysis: (1) assessment of the integration of circularity principles in the sets and their alignment with existing policy frameworks; (2) appraisal of quality and the fulfillment of the sets' functional purposes; (3) evaluation of the breadth and depth of tackled issues. Of the 27 EU member states, only nine have a dedicated bioeconomy strategy, of which four propose an indicator set. While there is a general lack of sophisticated monitoring, the tools proposed after the publication of the 2018 bioeconomy strategy (Germany and Italy) follow indicator development standards rigorously. They include circularity in their notion of bioeconomy and combine indicators for a comprehensive, substantial, informative and politically relevant analysis. These characteristics strongly improve the potential for alignment and coherence with urban-level bioeconomy monitoring efforts. Although national measuring tools are not intended to cover all urban needs, the findings of this paper give insight into their remaining gaps and highlight improvement pathways for an efficient EU-wide circular bioeconomy transition.

Recent trends in hyperthermophilic enzymes production and future perspectives for biofuel industry: A critical review

Charcoal production worldwide is increasing for energy use in households and industry, but it is often regarded as an unsustainable practice and is linked to agricultural frontiers (Prado 2000). The production (Coomes and Burt 1999) and use of charcoal in agriculture is common in Brazil and widespread in Asia (Steiner et al. 2004). The efficiency of biomass conversion into charcoal becomes important in conjunction with a newly proposed opportunity to use charcoal as a soil conditioner that improves soil quality on very acid and highly weathered soils (Lehmann et al. 2002; Steiner et al. 2004). This can be realized either by charring the entire aboveground woody biomass in a shifting cultivation system as an alternative to slashand-burn (coined recently as slash-and-char by (Glaser et al. 2002; Lehmann et al. 2002) or by utilizing crop residues in permanent cropping systems. Charcoal formation during biomass burning is considered one of the few ways that C is transferred to refractory long-term pools (Glaser et al. 2001a; Kuhlbusch and Crutzen 1995; Skjemstad 2001). Producing charcoal for soil amelioration instead of burning biomass would result in increased refractory soil organic matter, greater soil fertility and a sink of CO 2 if re-growing vegetation (secondary forest) is used. A farmer practicing slash and char could profit from soil fertility improvement and C credits (if provided by a C trade mechanism to mitigate climate change), providing a strong incentive to avoid deforestation of remaining primary tropical forests. Carbonised materials are formally authorized for use as soil amendment material in Japan, which is using 27% of its national charcoal production (50,835 t) for purposes other than fuel, more than 30.6% of which is used in agriculture (Okimori et al. 2003). In the past Japanese farmers prepared a fertilizer called “haigoe” which consisted of human waste and charcoal powder (Ogawa 1994). Charcoal is proposed to be an important component of the man-made and exceptionally fertile terra preta soils in the Amazon (Glaser et al. 2001b). This study examines the labour requirements, costs, income, production process and efficiency of making charcoal in rural communities in the Amazon near Manaus, Brazil. The charcoal making process, biomass conversion efficiency, the

Global energy security relies on fossil-based resources that are affiliated with the source of global warming, apart from punches of political and economic instabilities. Biomass is a promising alternative carbonaceous feedstock used for the production of clean energy that could have the potential to substitute for fossil fuels. This study aims to present a conceptual design that considers the criteria to identify the upper theoretical limits of biomass conversion, thus providing the potential approach to the conversion of three biomass (by-products: dry molasses, dry bagasse, and dry filter cake) through gasification, in order to contribute the biomass carbon-capturing by the model assessment of stoichiometric mass conversion and energy efficiency indicators into simple thermodynamic energy vectors, such as alcohols, alkanes, and syngas (a mixture of carbon monoxide and hydrogen). Modeling plays up the importance of stoichiometric efficiency of biomass conversion with the supply of oxygen and hydrogen. This realizes that the multi-product diversification of feedstock into syngas, hydrocarbons, and alcohol through integrated process schemes could have the potential to fill the energy gap and help to manage environmental load. In regard to biomass conversion results, the mass conversion and energy conversion efficiencies of dry bagasse have better conversion potential than molasses and F. cake (% mass conversion = 129 in syngas, 54.4 in alkane, and 43.4 in alcohol; % energy conversion = 94.3 in syngas and 93.3 in alkane and alcohol).

Methane fermentation of energy crops: Maximum conversion kinetics and in situ biogas purification

Multifunctional catalyst-assisted sustainable reformation of lignocellulosic biomass into environmentally friendly biofuel and value-added chemicals

Does circular bioeconomy contain singular social science research questions, especially regarding agriculture – industry nexus?