Bioenergy Production Potential Research Articles

Phenotypic Characterization of Citron Watermelon (Citrullus lanatus var. citroides) Genotypes for Bioenergy Production

Citron watermelon (Citrullus lanatus var. citroides) is an important climate smart crop, characterized by high oil content in the seeds and it is a popular fruit in southern Africa. To determine best performing genotypes eight phenotypic traits were assessed to identify cultivars with potential for biodiesel production. A field experiment was conducted at Sebele Agricultural Research Station, in Southern Botswana, during 2019 to 2020 cropping season. Four (4) melon genotypes were planted in a Randomized Complete Block Design replicated three times and eight (8) characters were assessed. Except seed oil content (26.6%) there was significant (P < 0.05) difference among all the traits, an indication of higher genetic diversity in the selected citron watermelon. SC1-Sesoswane, exhibited highest seed yield (1540 kg/ha) and oil yield (435.03 kg/ha) while MMB-280-Lerotse recorded lowest seed yield and oil yield of 548.1 kg/ha and 144 kg/ha respectively. There was a significant correlation of (0.9) between oil yield (kg/ha), number of fruits produced, and seed yield (kg/ha), an indication that increasing the seed yield will positively increase the amount of oil produced. This study revealed the potential bioenergy production of the four cultivars. However, SC1-Sesoswane appears a more promising alternative cultivar for feedstock for biodiesel production.

Mathematical modelling of quantifying bioethanol fuel production from pineapple waste

Lack of confidence in potential bioenergy production and net benefit hinders rapid implementations of such sustainable energy productions from different waste sources. With the aim of accelerating real-life implementations of more bioenergy productions, this paper presents development of a simple mathematical model, which can be used to evaluate potential bioethanol production capacity from pineapple waste under different input conditions. Based on an earlier experimental study, the mathematical model was developed depending on three contributing factors; pH, temperature and substrate concentration as considered in the earlier experimental study. Results from the developed mathematical formulation were compared with the experimental data from the earlier original study. It is found that the developed model is quite capable to estimate potential bioethanol productions from pineapple waste. Model estimated results are having a coefficient of correlation of 0.84 with the measured data. Standard errors of the model’s estimations are also quite low; RMSE = 0.49, MAE = 0.39 and RAE = 0.06. To facilitate a wider industrial generation, a basic mathematical model framework for economic analysis is proposed involving evaluation of net present values of expected future yields, as well as costs (initial and maintenance). Such mathematical model of economic analysis will help stakeholders on selecting optimum input parameters in achieving targeted benefit through optimised energy consumption.

Sweet Sorghum for Biofuel Production in Sub-Tropical India

Sweet sorghum (Sorghum bicolor L. Moench), a sugar crop with wider adaptation and high potential for bioenergy and ethanol production is expected to meet food, feed, fodder, fuel and fibre demands. It produces high biomass (50-80 t/ha) and alcohol (1500-2800 l/ha) and multiple income opportunities exist with this crop. Some sweet sorghum lines attain juice yields of about 78% of total plant biomass, containing from 15 to 23% soluble fermentable sugars which are composed mainly of sucrose (70–80%), fructose and glucose. Due to its short growing period (3-4 months), it could be cultivated and supplied during the lean period of sugarcane crushing thus extending the crushing period before and after sugarcane crushing and stretch the sugar mill operation. The major advantage with this crop is that no CAPEX is required when used in a sugar mill system as same machinery can be used for crushing and fermentation. It will help farmers to fetch additional income and provide an opportunity for better utilization of industrial facilities during sugarcane off-season. Promising sweet sorghum genotypes developed by ICAR-IIMR, Hyderabad are being tested for their suitability to sub-tropical conditions in February and June-July plantings at the NSI, Kanpur to establish a sustainable cropping system. Five sweet sorghum genotypes were tested during kharif 2021 for sweet sorghum productivity traits. The fresh stalk yield ranged from 45-60 t/ha and based on TRS, maximum alcohol percentage in wash was observed in three varieties, i.e., Phule Vasundhara, CSH 22SS and SSV 74 which was 8.4%, 8.38% and 7.8% respectively. Maximum ethanol yield of 53.05 L/T was recorded in CSH 22 SS followed by SSV 74 (50.93 L/T). Phule Vasundhara, with a highest stalk yield of 60 t/ha recorded highest ethanol content of 2837 L/ha followed by CSH 22SS (2780 L/ha) and SSV 74 (2411 L/ha).

Bioethanol Production from Marine Macroalgae Waste: Optimisation of Thermal acid Hydrolysis

AbstractMarine macroalgae waste, resulting from the accumulation of drifted algal biomass along the coastline, might be a relevant complementary raw material aiming sustainable bioethanol production. In the present study, the optimisation of thermal acid hydrolysis was performed using response surface methodology (RSM) considering the effect of three variables, namely, reaction time (10–60 min), acid concentration (0.1–2.5% (v/v) H2SO4) and biomass:acid ratio (5–15% (w/v)) on sugar concentration and yield. Under the best conditions, the resulting hydrolysates were fermented (7 days, 30 °C, 150 rpm, commercial yeast) to produce bioethanol. A statistically valid second-order model was obtained (r2 = 0.9876; Prob > F lower than 0.05), showing that sugar concentration is mostly influenced by the biomass:acid ratio while reaction time was not significant. The maximum predicted sugar concentration was 18.4 g/L, being obtained at 2.5% H2SO4 concentration and 15% (w/v) biomass:acid ratio, corresponding to a sugars yield of 12.5 g/100 g (less 36% than that obtained using 10% (w/v)). At the best conditions, the hydrolysates were fermented to obtain a bioethanol concentration up to 2.4 g/L and a 21 mgbioethanol/gbiomass yield, emphasizing the biomass potential for bioenergy production. Graphical Abstract

Sustainable biorefinery development for valorizing all wastes from date palm agroindustry

This study examined how various residues from date palm agroindustrial can be utilized in a biorefinery platform to produce ethanol, methane, and lignin. Liquid hot water, ethanol organosolv, and catalyzed ethanol organosolv (CEO) pretreatments were applied to trunk, leaves, leaf sheath, pedicels, date cake, and seeds. The process included extracting lignin from the liquid fraction, followed by converting the pretreated solid material into ethanol. The fermentation residues were also utilized to produce biomethane through anaerobic digestion. Two different scenarios were employed for the biorefining, i.e., (Ⅰ) maximum lignin production and (Ⅱ) maximum biofuel production. The best results for the first scenario were obtained when CEO was employed in the pretreatment of date palm wastes, where 806.9 mL ethanol, 902.8 L methane, and 528.0 g lignin were produced from each kg of each residue. In energetic terms, the biofuel products (i.e., ethanol and methane) were determined to have a combined energy content equivalent to 1553.1 mL of gasoline. Likewise, the most favorable outcomes of the second scenario were obtained by incorporating CEO pretreatment of trunk, leaf sheath, leaves, and pedicels in the valorization of untreated date cake and seeds. Furthermore, for the second scenario, the resulting products were 967.5 mL ethanol, 1605.3 L methane, and 341.0 g lignin, with the biofuel products having a combined energetic content equivalent to 2452.0 mL of gasoline. These findings indicate that the biorefining of date palm agroindustrial wastes has significant potential for bioenergy production.

Water footprint approach in measuring the potential of bioenergy production from agricultural products

Abstract Promoting the supply of energy from biomass to reduce the emission of greenhouse gases has resulted in focusing on the production of important products from the perspective of energy and, ultimately, increasing water consumption. Therefore, in the present study, an index called water footprint was used to investigate the link between water and bioenergy. For this purpose, information related to grain maize crops was collected in the study plains of Fujian Province in eastern China. Based on the calculations, it was found that the water footprint of maize products in the province was equal to 3,728 m3/ton on average, and the water footprint of its biomass was estimated to be 219.6 m3/ton. Moreover, the investigation of the water footprint of maize biomass energy showed that the highest and lowest water footprints per unit of energy are found in Ningde and Zhangzhou, respectively. It was also found that the plains of Zhangzhou, Ningde and Xiamen have little priority for biomass production because the water footprint of their biomass energy is less than 900 MJ/m3. On the other hand, Nanping and Putian plains with bioenergy water footprints between 1,500 and 1,800 MJ/m3 have high priority for using maize biomass for energy production.

Carbon-neutral potential in treatment of N, N-dimethylformamide-containing industrial wastewater: Comparative investigation of energy conservation, carbon reduction and expenditure between UASB and Fenton process

The methanogenic degradation of N, N-dimethylformamide (DMF) is a sustainable and low-carbon technology for the treatment of high-strength industrial wastewater. Compared with the state-of-the-art chemical degradation method like Fenton, the UASB process exhibited its promising superiority in bio-energy recovery, economic profit gaining and carbon emission reduction. The lab-scale UASB obtained high DMF removal efficiency of over 98 % with methane recovered as bio-energy at a limited organic loading rate (OLR) of 4.2 COD kg/m3/d. Compared with the Fenton process, the UASB process is demonstrated more suitable to the carbon-neutral treatment of high-strength DMF-containing wastewater: The Fenton process is suitable to the relative low COD concentration below 1500 mg/L; The UASB was capable of covering all electricity consumption when COD > 3586 mg/L; The UASB also achieved zero CO2 emission when COD > 5720 mg/L; The UASB process obtains net profit when COD > 3616 mg/L. This study provided clear evidence of the promising potential and remarkable feasibility of bio-energy production in carbon-neutral treatment of DMF-containing wastewater.

Comprehensive Characterization of Kukui Nuts as Feedstock for Energy Production in Hawaii.

Fuel properties of oil-bearing kukui (Aleurites moluccana) nuts, a commonly found crop in Hawaii and tropical Pacific regions, were comprehensively studied to evaluate their potential for bioenergy production. Proximate and ultimate analyses, heating value, and elemental composition of the seed, shell, and de-oiled seed cake were determined across five sampling locations in Hawaii. The aged and freshly harvested kukui seeds were found to have similar oil contents, ranging from 61 to 64%wt. Aged seeds, however, have 2 orders of magnitude greater free fatty acids than those freshly harvested (50% vs 0.4%). The nitrogen content of the de-oiled kukui seed cake was found to be comparable to that of the soybean cake. Aging of kukui seeds can decrease the flashpoint temperature and increase the liquid-solid phase transition temperatures of kukui oil obtained. Mg and Ca are the major ash-forming elements present in the kukui shells, >80%wt of all metal elements detected, which may reduce deposition problems for thermochemical conversion in comparison with hazelnut, walnut, and almond shells. The study also revealed that kukui oil has similar characteristics to canola, indicating that it is well-suited for biofuel production.

Eastern red cedar effects on carbon sequestration and soil quality in the Great Plains

AbstractEastern red cedar (ERC, Juniperus virginiana L.) is a common tree species in agroforestry plantings and has great potential for bioenergy production due to physical and chemical characteristics of its biomass. The objective of this study was to assess the effects of ERC plantings on carbon (C) sequestration and selected soil quality parameters in existing plantings across the northern U.S. Great Plains. Nine locations were selected in five states with mean annual precipitation (MAP) from 446 to 999 mm and mean annual temperature (MAT) from 4.4 to 10.0°C. Infiltration was measured using the twin ring technique at nine sites in each tree planting and adjacent field (crop, pasture, or hay) at each location. Following infiltration measurements, a 4.8 cm‐diameter soil core to 30 cm depth was collected from inside one infiltration ring of each pair for bulk density, pH, aggregate stability, soil organic carbon (SOC), and total nitrogen (TN) analyses. Penetration resistance in 2.5 cm increments to 30 cm depth was measured in the other infiltration ring. SOC stocks under ERC were significantly higher than in the adjacent field soil at five of the locations and, for all locations, averaged 16.8% greater than in the adjacent field. The estimated SOC accumulation rate for the eight locations with uniform tree stand age averaged 0.30 Mg C ha−1 year−1. Most locations had higher TN and C/N and lower bulk density beneath ERC. Fewer differences for infiltration and penetration resistance and smaller and less consistent differences for pH and aggregate stability were observed. Tree aboveground C stocks were estimated to increase an average of 2.05 Mg C ha−1 year−1. Estimated tree aboveground biomass C and SOC stocks under ERC and in adjacent fields were strongly correlated with MAP. Potential ERC planting for C sequestration or bioenergy feedstock production is not likely to significantly degrade soil quality and may improve soil physical or chemical quality for locations in the US Great Plains.

Benefit analysis of multi-approach biomass energy utilization toward carbon neutrality

To reduce greenhouse gas (GHG) emissions, biomass has been increasingly developed as a renewable and clean alternative to fossil fuels because of its carbon-neutral characteristics. China has been investigating the rational development and use of bioenergy for developing its clean energy and achieving carbon neutrality. Substituting fossil fuels with multi-source and multi-approach utilized bioenergy and corresponding carbon reduction in China remain largely unexplored. Here, a comprehensive bioenergy accounting model with a multi-dimensional analysis was developed by combining spatial, life cycle, and multi-path analyses. Accordingly, the bioenergy production potential and GHG emission reduction for each distinct type of biomass feedstock through different conversion pathways were estimated. The sum of all available organic waste (21.55 EJ yr-1) and energy plants on marginal land (11.77 EJ yr-1) in China produced 23.30 EJ of bioenergy and reduced 2,535.32 Mt CO2-eq emissions, accounting for 19.48% and 25.61% of China's total energy production and carbon emissions in 2020, respectively. When focusing on the carbon emission mitigation potential of substituting bioenergy for conventional counterparts, bioelectricity was the most effective, and its potential was 4.45 and 8.58 times higher than that of gaseous and liquid fuel alternatives, respectively. In this study, life cycle emission reductions were maximized by a mix of bioenergy end uses based on biomass properties, with an optimal 78.56% bioenergy allocation from biodiesel, densified solid biofuel, biohydrogen, and biochar. The main regional bioenergy GHG mitigation focused on the Jiangsu, Sichuan, Guangxi, Henan, and Guangdong provinces, contributing to 31.32% of the total GHG mitigation potential. This study provides valuable guidance on exploiting untapped biomass resources in China to secure carbon neutrality by 2060.

Farmers’ preferences and willingness to adopt anaerobic digestion technologies: a case study in rural areas in Colombia

Although Colombia has a great potential for bioenergy production, the national energy matrix still has gaps and challenges when it refers to the promotion, adoption, and implementation of renewable sources of energy. In this study, we investigated the preferences of the local farmers and their willingness to adopt biogas technologies. Based on the results obtained, a protocol for the adoption of biodigesters by small farmers was proposed. The results obtained in this study show that the majority of the respondents of this study are the owners of their land, and use it mainly for agricultural purposes. Although about 56% of the inquiries do not have enough knowledge on how to obtain biogas from agricultural or livestock waste, about 93% are willing to use gas/biogas technologies instead of using firewood and other dry organic waste. Based on the results obtained in this study a protocol to support the development and implementation of biogas technologies in the rural areas of Colombia was proposed, taking into account the bioenergy potential available and the profile of the farmers.

Assessment of bioenergy and syngas generation in India based on estimation of agricultural residues

India possesses a huge potential in biomass power generation to reduce dependency on fossil fuel imports. Of the available biomass sources, crop residues are particularly interesting as they dispersed resources with varying spatiotemporal availability and features. These residues also have competing applications which differ geographically. In India, state-wise crop-level biomass databases are found to be scarce, and local biomass records are critical to implement decentralized bioenergy projects. The main objective of this study is to critically assess the potential of agricultural crop residues, their subsequent bioenergy, and the syngas production potential in all of India’s regions (28 states and 8 UTs). 43 major crop residues produced from 28 different crops produced in different regions of India were taken for this study, considering their recent crop production statistics for the year 2017-18 and following standard estimation procedures. The syngas production potential was estimated using a Python gasification model using input parameters from the literature.Overall, 869.11 MT of gross residue is generated annually, with 288.14 MT (33.15%) of surplus residue. In terms of surplus crop residue, Uttar Pradesh produces the most surplus residue (57.72 MT) and sugarcane ranks first with a national potential of 62.68 MT. For the 2017-18 fiscal year, the bioenergy production potential from surplus crop residue was estimated to be 4.88 EJ. This syngas generation potential is determined to be 37.64% of India’s gross residual potential. Upgrading this quantity of syngas via, for example, methanol (MeOH) synthesis is expected to provide 81.7905 MT of MeOH with an equivalent energy content of 1.85 EJ.

Sanitary Wastewater Supplemented with Glycerol to Obtain Lipid-Rich Microalgal Biomass

Introduction: Mixotrophic microalgae systems have great potential for bioenergy production and wastewater treatment. Anaerobic-treated wastewater supplemented with carbon can improve biomass yield and quality, as it presents low carbon content. Alternative carbon sources in microalgae cultivation, such as glycerol, are essential for minimizing the economic and environmental impacts caused by biomass production, and improving the profile of fatty acids. This study aimed to increase biomass production and the lipid content with glycerol as the carbon source for microalgae cultivation from sanitary wastewater.
 Materials and Methods: The microalgae behavior in the wastewater was pilot tested using glycerol supplementation at 7.5, 10.5, and 12.5 g L-1.
 Results: In all the experiments with sanitary wastewater, the microalgae production presented Chlorella sp. as the predominant species. The best biomass (3.78 ± 1.12 g L-1) and lipid (35.67 ± 0.80%) yields were found at 12.5 and 10.5 g L-1 of glycerol, respectively.
 Conclusion: The microalgae produced more lipids with glycerol supplementation. An attractive profile for biodiesel was found regarding the fatty acids in the biomass.

Physicochemical analysis and intermediate pyrolysis of Bambara Groundnut Shell (BGS), Sweet Sorghum Stalk (SSS), and Shea Nutshell (SNS)

ABSTRACT The current work focused on the intermediate pyrolysis of Bambara Groundnut Shells (BGS-G1), Sweet Sorghum Stalk (SSS), and Shea Nutshells (SNS). These feedstocks are readily available as wastes or by-products from industrial and agricultural activities. The thermo-gravimetric analysis of the biomass samples exhibited decomposition and devolatilization potentials in the temperature range of 110–650°C. The kinetic modelling resulted in the activation energy of BGS G1 being the lowest as 20.43 kJ/mol and SNS as the highest 24.89 kJ/mol among the three biomass samples. Intermediate pyrolysis was conducted in a vertical tube reactor at a temperature of 600°C, with nitrogen flow at 10 ml/min and heating rate ≥ 33.0℃/min. The yield of pyrolysis bio-oil was 38.0 ± 6.4, 44.2 ± 6, and 39.7 ± 5.2 wt.% for BGS-G1, SSS, and SNS, respectively. The HHV of bio-oil varied as 23.7 ± 1.8, 23.8 ± 1.8, to 26.5 ± 2.0 MJ/kg for BGS-G1 SSS and SNS respectively. The biochar recorded the lowest HHV for BGS-G1 as 18.8 ± 1.2 MJ/kg and the highest for SNS as 26.4 ± 1.8 MJ/kg. The FTIR of bio-oil revealed significant functional groups, and GC-MS (Gas Chromatography and Mass Spectrometry) analysis categorized the compounds in bio-oils as ketones, furans, phenolics, acids, phenols and benzene derivatives. The physicochemical analysis of the feedstocks and the products (bio-oil and biochar) showed their potential for bioenergy and biochemical (green chemicals) production.

Chemical composition and species identification of microalgal biomass grown at pilot-scale with municipal wastewater and CO2 from flue gases

The production potential of a locally isolated Chlorella vulgaris strain and a local green-algae consortium, used in municipal wastewater treatment combined with CO2 sequestration from flue gases, was evaluated for the first time by comparing the elemental and biochemical composition and heating value of the biomass produced. The microalgae were grown in outdoor pilot-scale ponds under subarctic summer conditions. The impact of cultivation in a greenhouse climate was also tested for the green-algae consortium; additionally, the variation in species composition over time in the three ponds was investigated. Our results showed that the biomass produced in the consortium/outdoor pond had the greatest potential for bioenergy production because both its carbohydrates and lipids contents were significantly higher than the biomasses from the consortium/greenhouse and C. vulgaris/outdoor ponds. Although greenhouse conditions significantly increased the consortium biomass's monounsaturated fatty acid content, which is ideal for biodiesel production, an undesirable increase in ash and chemical elements, as well as a reduction in heating value, were also observed. Thus, the placement of the pond inside a greenhouse did not improve the production potential of the green-algae consortium biomass in the current study infrastructure and climate conditions.

Thermal degradation of emerging contaminants in municipal biosolids: The case of pharmaceuticals and personal care products

The presence of emerging contaminants in water and wastewater resources is of ongoing concern for public health and safety. Pharmaceutical compounds are designed to be biologically active and therefore may have effects on nontarget organisms in terrestrial and aquatic environments, even at trace concentrations. The presence of pharmaceutical and personal care products (PPCPs) in wastewater treatment plants is reported in various countries worldwide, mostly in the levels of nanograms to micrograms per litre. The present study investigates the thermal degradation of municipal sewage sludge containing PPCPs at various heating rates. The examined characteristics of the samples include thermal decomposition behavior, volatile release characteristics, and pyrolytic product composition. Thermal characterization of the PPCPs was conducted using differential scanning calorimetry. The gaseous products and typical functional groups of the released volatiles detected by Fourier-transform infrared spectroscopy mainly contained CO2, CO, small-chain hydrocarbons, and oxygen- and nitrogen-containing functional groups together with other species. In addition, the potential of bioenergy production was investigated as a spin-off opportunity during thermal degradation of biosolids. Study results showed that PPCP concentrations can be lowered significantly by thermal treatment of municipal biosolids. Antifungal/antibacterial agents together with opioids, in particular triclosan and tramadol, showed less resistance to thermal degradation while antibiotics could be more recalcitrant to heat treatment. The thermodynamic results provide an important reference for future reactor design and the thermochemical treatment of biosolids as well as their conversion to value-added products.

Halimione portulacoides biomass - a sustainable feedstock for bioenergy production from an integrated water-energy-food system

In view of a water-energy-food (WEF) nexus strategy, the present work assessed the bioenergy production potential of Halimione portulacoides used for the phytoremediation of nutrient-rich simulated wastewater from saltwater-based integrated multi-trophic aquaculture (IMTA). Specimens of this halophyte plant were grown in hydroponics under four different nutrient treatments with distinct nitrogen (N) and phosphorous (P) concentrations. Ultimate and proximate analysis, calorific value and thermogravimetric analysis coupled to mass spectrometry were used to assess the bioenergy potential of the non-edible biomass of the plants, namely the canes (C) and roots (R), and of commercial pellets (CP), which were used as benchmark. R and, especially, CP had higher carbon but lower oxygen content and larger volatiles but lower ashes than C. The higher heating values (HHV) of C (16–17 MJ kg−1) and R (17–18 MJ kg−1) were the same order as those of conventional energy crops and CP (20 MJ kg−1). Although mass loss and associated gaseous emissions during temperature programmed pyrolysis occurred mainly between 250 and 650 °C for all biomasses, they took place at slightly higher temperatures for C > CP > R. In any case, the integrated gaseous emissions during the pyrolysis of C, R, and CP were very similar and included H2, CH4, CO, and CO2 (syngas main constituents). Biomass production of C was affected by the nutrients load of the applied treatments, but this was not the case for R. Also, the nutrients treatments had no detectable effects on the biomasses’ ultimate or proximate analysis, HHV, thermal decomposition or resultant gaseous emissions. Thermal properties and behaviour of C and R were very similar to those of CP, showing their potential for bioenergy production and revealing that a WEF nexus strategy can be implemented in IMTA by energetic valorization of non-edible biomass of H. portulacoides used for water phytoremediation.

An accelerated approach of biogas production through a two-stage BioH2/CH4 continuous anaerobic digestion system from Napier grass

Napier grass found to be greatest potential for gaseous bioenergy production. The biohydrogen and biomethane productions from untreated Napier grass in single and two-stage continuous bioreactors was evaluated using anaerobic digestion technology. The bioreactors were fed Napier grass with organic loading rate (OLR) of 0.5, 1.0 and 2.0 kg VS/m3-d, respectively. The hydrogen, methane, and energy yields were evaluated. The methane yield of single-stage system was 282.08 CH4/g vS with OLR of 0.5 kg VS/m3-d. For two-stage system, the biohydrogen and biomethane yields were 90.06 mL H2/g vS and 367.00 mL CH4/g vS with OLRs of 1.0 and 0.5 kg VS/m3-d, respectively. The energy yields of single and two-stage systems were 13.14 and 10.10 kJ/g vS respectively. The peak OLR of Napier grass was 0.5 kg VS/m3-d for the two-stage system whereas the total energy recovery was 30 % higher than the single-stage system.

Sustainable development in China: Valuation of bioenergy potential and CO2 reduction from crop straw

Bioenergy is recognized as a promising alternative for future energy demand and decarbonization development. Crop straw, especially wheat, rice, and maize straw, is one of the significant feedstocks for bioenergy production. However, the production potential of different types of bioenergy from crop straw, and its potential to reduce CO2 emissions are poorly understood. Thus, we collected crop straw utilization data at the provincial level via face-to-face field surveys to estimate straw quantity until 2030, dividing the 31 provincial regions in mainland China into four regions each for wheat (W-I, II, III, IV), rice (R-I, II, III, IV), and maize (M-I, II, III, IV), respectively, based on their quantity and distribution. The results show that if all three types of straw are used for bioenergy production, the bioenergy production potential is 75.1 Mtce for electricity, 151.5 Mtce for bioethanol, 182.1 Mtce for biomethane, and 329.1 Mtce for briquette fuel in 2030. Substituting electricity, bioethanol, biomethane, and briquette fuel for fossil fuels could reduce CO2 emissions by 562.9, 362.4, 220.4, and 1654.2 Mt, respectively. Our study indicates that wheat straw should be used for bioethanol and electricity production, maize straw for electricity and briquette fuel, and rice straw for biomethane. This research provides a good reference for local and national governments for policy formulation regarding straw utilization, and it will also help bioenergy plants select the best plant locations, bioenergy types, and feedstock types to obtain a high quantity of bioenergy and realize decarbonization development.

Fungal communities represent the majority of root-specific transcripts in the transcriptomes of Agave plants grown in semiarid regions.

Agave plants present drought resistance mechanisms, commercial applications, and potential for bioenergy production. Currently, Agave species are used to produce alcoholic beverages and sisal fibers in semi-arid regions, mainly in Mexico and Brazil. Because of their high productivities, low lignin content, and high shoot-to-root ratio, agaves show potential as biomass feedstock to bioenergy production in marginal areas. Plants host many microorganisms and understanding their metabolism can inform biotechnological purposes. Here, we identify and characterize fungal transcripts found in three fiber-producing agave cultivars (Agave fourcroydes, A. sisalana, and hybrid 11648). We used leaf, stem, and root samples collected from the agave germplasm bank located in the state of Paraiba, in the Brazilian semiarid region, which has faced irregular precipitation periods. We used data from a de novo assembled transcriptome assembly (all tissues together). Regardless of the cultivar, around 10% of the transcripts mapped to fungi. Surprisingly, most root-specific transcripts were fungal (58%); of these around 64% were identified as Ascomycota and 28% as Basidiomycota in the three communities. Transcripts that code for heat shock proteins (HSPs) and enzymes involved in transport across the membrane in Ascomycota and Basidiomycota, abounded in libraries generated from the three cultivars. Indeed, among the most expressed transcripts, many were annotated as HSPs, which appear involved in abiotic stress resistance. Most HSPs expressed by Ascomycota are small HSPs, highly related to dealing with temperature stresses. Also, some KEGG pathways suggest interaction with the roots, related to transport to outside the cell, such as exosome (present in the three Ascomycota communities) and membrane trafficking, which were further investigated. We also found chitinases among secreted CAZymes, that can be related to pathogen control. We anticipate that our results can provide a starting point to the study of the potential uses of agaves’ fungi as biotechnological tools.