Green Biorefinery Research Articles

Green biorefinery of walnut husk: Phenolic extraction and ethanol production

Microwave and ultrasound techniques were utilized on walnut green husk (WGH) to extract valuable phenolic compounds and enhance the residual biomass's susceptibility to hydrolysis for subsequent ethanol production. The aim was to optimize process variables in order to achieve an integrated biorefinery with the zero-waste-base standpoint. For microwave-assisted extraction (MAE), four-time levels (0.5, 1.0, 2.0, and 5 min) and power settings (300, 450, 600, and 800 W) were tested. Ultrasound-assisted extraction (UAE) was conducted at a frequency of 28 kHz and power of 100 W over varying time intervals (2, 6, 10, 14, 18, and 22 min). Generally, higher power settings and longer extraction times produced higher contents. Specifically, the maximum total phenolic content (TPC) (220.13 mg GAE/g-DW), total flavonoid content (TFC) (63.21 mg catechin/g-DW), and DPPH scavenging activity (86.13 %) were achieved using the highest power and longest extraction time for MAE. Similarly, the longest UAE time resulted in the highest TPC (214.32 mg GAE/g-DW), highest TFC (58.44 mg catechin/g-DW), and DPPH scavenging activity (76.15 %). Moreover, increased microwave power and longer extraction times favored glucose and ethanol yields, with maximum yields of 55.30 % and 36.67 %, respectively, obtained at 800 W for 5 min. For UAE, the highest glucose and ethanol yields (52.33 % and 34.16 %, respectively) were obtained at 22 min. Conversely, lower extraction times and power settings for microwave, as well as shorter ultrasound times, were beneficial for lignin removal. The application of MAE and UAE in the WGH biorefinery process enhanced the extraction of phenolics and improved biomass hydrolysis, leading to more efficient, sustainable, and economically viable production of biofuels and bioproducts.

Assessing the environmental footprint of alternative green biorefinery protein extraction techniques from grasses and legumes

The significant grasslands of Europe and its member states represents a significant feedstock opportunity for circular bioeconomy development. The development of green biorefineries (GBR), to supply protein for the feed industry from grass, could help many European member states to address significant deficits in protein availability and reduce imports. The current study assesses the environmental footprint of alternative GBR protein extraction techniques from grasses and legumes using life cycle assessment. The focus is on comparing feedstock and technology pathways that could displace soya bean imports. The study finds that leaf protein concentrate (LPC) produced from grass had an improved environmental performance when compared to soya bean meal (SBM), across the assessed feedstock (perennial ryegrass or grass-clover mixtures) and technology pathways (one-stage maceration versus multi-stage maceration). For example, in the case of Climate Change the emission intensity for LPC was 57–85 % lower per tonne of crude protein (CP) compared with SBM. Acidification burdens were 54–88 % lower, and Eutrophication: Freshwater burdens were 74–89 % lower. Some scenarios of GBR produced LPC with a larger Energy Resources: Non-Renewable burden than SBM, though this could be mitigated with higher renewable energy (biogas and wind energy) integration within the scenario. Grass-clover scenarios generally achieved a lower intensity of emissions compared to ryegrass scenarios, particularly in the category of Climate Change, where feedstock cultivation represented a significant contributor to impacts. Overall, GBR can produce high quality protein with a lower environmental burden than SBM, but choice of feedstock and system design are critical factors for overall environmental performance.

Tailoring defoliation and nitrogen management for large canopy radiation use and biomass production of perennial systems destined for biorefinery

Perennial leafy grasses and legumes are promising for extraction of proteins with a green biorefinery amid increasing demand for local production. However, which defoliation strategy increases radiation-use efficiency and biomass production still needs to be determined. A multi-year field experiment started in 2019 in Denmark with fertilized grasses (perennial ryegrass, tall fescue), unfertilized legumes (alfalfa, red clover) and their fertilized mixture (grass-legume), each defoliated at 2-, 4- or 8- weeks interval, at either 7-9 or 12-14 cm defoliation height. The main aim was to quantify effects of species, defoliation height and frequency, and nitrogen application rate on canopy radiation interception, aboveground biomass and crude protein production, as well as aboveground radiation use efficiency (RUEA).The results showed that accumulated intercepted photosynthetically active radiation (AIpar) increased with increasing defoliation height and decreasing frequency for most systems, with the largest AIpar obtained seasonally by red clover (730-815 MJ m−2) and grass-legume mixture (790-826 MJ m−2) defoliated at medium to low frequency. Tall fescue defoliated at medium to low frequency yielded the highest aboveground biomass (10-14 Mg ha−1) and red clover defoliated at medium to high frequency yielded the most crude protein (2.5-2.9 Mg ha−1) compared to all other systems annually. RUEA decreased with increasing defoliation height and maximum values were achieved at medium frequency, with tall fescue having significantly higher RUEA (1.6-2.1 g MJ−1) than the other systems. Seasonally, RUEA was variable at high defoliation frequency, being consistently higher at the start and the end of the season for ryegrass and the mixture systems.This study pinpoints tall fescue and red clover as perennial crops with high agronomic productivity among tested species for green biorefinery and also concluded that red clover in temperate humid climate maximize productivity and sustainability for biorefining with defoliation at low height and medium frequency.

Arachis pintoi Krapov. & W.C. Greg.–A multifunctional legume

AbstractArachis pintoi, commonly known as pinto or forage peanut, is used mainly in consortia with grass pastures and as cover plant. In addition to increasing the productivity of livestock and plantations, it contributes to the mitigation of environmental impacts (reduction of greenhouse gas emissions) and soil improvement (nitrogen fixation, reduction of fertilizers use), as well as to pests and disease management. Several cultivars that are tolerant to specific climates and soil conditions are suitable to be used as ground covers in agroforestry and silvopastoral systems, orchards, and plantations. Biotechnological and phytochemical investigations revealed the potential of pinto peanut as a sustainable source of resveratrol and other stilbenoids. Extracts from plants grown under natural conditions and from materials obtained in vitro displayed allelopathic, anthelmintic, or antioxidant activities. Other studies revealed the potential of pinto peanut for erosion control, phytoremediation, seed and essential oils production, materials for animal tissue engineering, synthesis of nanoparticles for drug delivery, and as green biorefineries to produce proteins, biochemicals, and biomaterials.

Forage type and additive effects on fermentation quality and biorefinery performance of silages

AbstractThe concept of a green biorefinery has recently gained interest and can be defined as a process where green biomass is processed to a variety of products. Most green biorefineries rely on fresh green biomass as the feedstock, but using a stable ensiled biomass could provide benefits. We evaluated the effects of silage additive treatments on silage fermentation quality and performance in a laboratory scale liquid–solid separation to simulate the first step of a green biorefinery. In Experiment 1, red clover and fresh and wilted grass were ensiled without additive or treated with a lactic acid bacteria inoculant or a formic acid based additive. In Experiment 2, grass or red clover were treated with a fibrolytic enzyme, formic acid or a combination of them, and a control without additive was also included. Silage fermentation quality was improved by additive use. Biomass dry matter concentration was negatively related to liquid yield, but effects of additive treatments on the biorefinery performance were minor and inconsistent between different forages. Optimizing agronomic and feedstock conservation management plays an important role for the success and sustainability of the biorefinery process. Good silage management practices with minimal losses during storage should be targeted, but no clear patterns in biorefinery outputs were observed in the current study when different types of additives were used in grass and clover silage production.

A novel green biorefinery strategy for corn stover by pretreatment with weak alkali-assisted deep eutectic solvents

The strategy using deep eutectic solvent–sodium bicarbonate (DES–SB) has achieved a high delignification efficiency, excellent carbohydrate digestibility (glucose yield, 97.47%; xylose yield, 92.93%), and regenerated lignin with great potential.

From residue to resource: The recovery of high-added values compounds through an integral green valorization of citrus residual biomass

Exploitation of residual citrus biomass in biorefineries should include extraction of bioactive compounds, with particular attention to the high extractable content of this by-product. In fact, according to the principles of biorefinery, transforming “waste” to “secondary raw material” can totally or partially reduce the economic and ecological issues. In this study, green residual biomass from citrus trees located in a Capbon peninsula region (Tunisia) was analyzed. A phytochemical study was carried out by determining the content of polyphenols and flavonoids and antioxidant activities. Gas chromatography coupled with time-of-flight mass spectrometry (GC-TOFMS) analysis allowed the identification and evaluation of bioactive compounds as quinic acid, proline, alpha-linolenic acid and alpha-amyrin known for their wide range of applications. In addition, the fragrant aroma composition of petitgrain essential oil displayed substantial qualitative and quantitative differences that could serve as a promising natural source used in the development and formulation of functional foods and pharmaceutical products, in flavoring, liqueurs, perfumes, and medicines of ingredients. Then, the hydrodistillation effluent was assessed for its antioxidant and antifungal potential from where it is proven that it could be a source of the bioactive compounds with high spectrum of biological activities. From the point of view of the integral valorization of these underexploited and wasted bioresidues offers the double opportunity to recover biosourced molecules with high added value on the one hand and to reduce the pollutant effects on the other hand, and thus, contributing to promoting sustainable development and bioeconomy via a zero waste integrated approach priming the green biorefineries pathways.

Green biorefinery of shrimp shell waste for α-chitin and high-value co-products through successive fermentation by co-lactic acid bacteria and proteolytic fungus

Green biorefinery process was conducted to extract α-chitin and high-value co-products from shrimp shell waste through microbial fermentation using mature coconut water (MCW) as a sole nutrient source. Symbiotic co-lactic acid fermentation (Co-LAF) by Lactobacillus plantarum and Streptococcus thermophilus produced higher levels of lactic acid (LA) and protease activity than their mono-cultures, which led to greater demineralization (DM) and deproteinization (DP) of shrimp shell powder (SSP). After optimizing Co-LAF through Response Surface Methodology and successive fermentation by an acid-active proteolytic fungus Rhizopus oligosporus, the highest DM of 94.0 ± 0.91 % and DP of 86.7 ± 0.1 % were achieved. Based on FT-IR, XRD, and SEM analysis, the bio-extracted chitin had similar structural characteristics to commercial α-chitin but with better quality. These strategies not only contribute to environmentally-friendly and cost-effective extraction of α-chitin (303 ± 18 mg/g-SSP), but also co-produce LA (57.18 ± 0.89 g/L), acid protease (4.33 ± 0.5 U/mL), bio-calcium (277 ± 12 mg-CaSO4/g-SSP), protein hydrolysate (268 ± 5 mg/g-SSP), and pigments (28.78 ± 1.56 µg/g-SSP).

Sequential extraction of fucoidan, laminarin, mannitol, alginate and protein from brown macroalgae Ascophyllum nodosum and Fucus vesiculosus

The study involves development of a green biorefinery process for obtaining fucoidan, laminarin, mannitol, alginate and protein from dry and fresh Fucus vesiculosus and Ascophyllum nodosum using hydrochloric acid and a green extraction solvent. After the extraction of fucoidan which was the targeted biomolecule, an extract and by-product (residual biomass) were obtained. The extract was passed through an ultrafiltration membrane, where fucoidan was obtained in the ultrafiltration retentate while ultrafiltration permeate was analysed for laminarin and mannitol. The residual biomass was used for obtaining alginate using ultrasound (20 kHz, 64 % amplitude and 32 min, optimum parameters for alginate extraction based on our previous study). All the samples, showed good results for alginate, laminarin and mannitol, indicating that the by-products can be utilised using this green extraction process. The comparison of both dry and fresh seaweed is relevant from an industry perspective, as fresh seaweed can directly be used for extraction, avoiding drying which adds significantly to the cost of the process. Life cycle impact assessment of the complete seaweed value chain has been carried out to identify the energy demand and key environmental hotspots. This biorefinery process can be used by industry to improve their processes and utilise the by-products generated efficiently.

Biorefinery integration of a green protein platform for maximum resource utilization

Biorefineries are often proposed to reduce environmental impact, enhance energy independence, and minimize waste generation while generating multiple valuable products. In this work, an integrated biorefinery approach is proposed to improve the overall process performance of a system combining a green biorefinery (GB), hydrothermal liquefaction (HTL), and anaerobic digestion (AD) to produce a leaf protein concentrate, bio-crude, and biogas. Festulolium and ryegrass, two varieties of forage grasses, were employed as feedstock. Two different maceration technologies were evaluated for protein recovery, more severe maceration led to a 75 % increase in protein content in the leaf protein concentrate (LPC) when compared to a standard maceration. The fiber residues produced by the grass processing were converted to biocrude using HTL. This step was not affected by the maceration step and the use of brown juice as HTL media proved to be beneficial. The bio-crude yield of the grass fiber residues was similar for both biomasses and maceration steps, ranging from 25.7 to 32.1 %. Finally, the HTL process water and the brown juice were subjected to anaerobic digestion to produce biogas. The brown juice from ryegrass resulted in higher methane production compared to HTL water but adding brown juice to HTL water did not reduce the lag times observed for pure HTL water. The integration of GB, HTL, and AD is shown to be effective in increasing the overall carbon and nitrogen recovery of the starting biomass.

Environmental impacts of a novel biorefinery platform integrated with power-to-protein technology to decrease dependencies on soybean imports

The consistent population growth is directly tied to the annual rise in livestock production, placing a substantial burden on the crop sector that supplies animal feed. The Danish government has been relying on importing soybeans and soybean meal to be used as animal feed. However, this sparked environmental concerns that require more environmentally friendly solutions, such as self-sufficiency in animal feed production. The rise of green biorefineries allows new avenues of animal proteinaceous feed production using green biomass to produce leaf protein concentrate (LPC) and utilize side-stream products, such as brown juice and press cake, for feed-quality products. This study evaluated the combination of grass-clover biorefinery and the power-to-X concept, including power-to-protein technology, for its environmental sustainability through a consequential life cycle assessment (CLCA). The production of protein concentrate from organic grass clover exhibits optimal environmental performance when press cake and brown juice are used for bioenergy recovery. The findings indicate that combining a green biorefinery with power-to-protein to fully valorize the carbon and nitrogen content of brown juice and press cake into feed-grade protein can increase the environmental benefits. Such an integration resulted in an avoided impact of −995.9 kg CO2-eq/tonne of protein concentrate. The avoided impacts of climate change could be higher within the first 20 years due to a higher carbon sequestration rate. However, even after 20 years when a new carbon balance in the soil is reached, the environmental gain could be big enough to encourage the production and use of organic grass-clover protein concentrate.

Technology development and challenges for the transformation of municipal solid waste into sustainable energy production

Municipal solid waste (MSW) disposal methods that are not under control, such as open burning, unrestricted incineration, landfilling and dumping into water bodies, pose a severe hazard to the environment and public health. As a result, the development of cheap and ecologically suitable disposal methods is currently extensively demanded by the expanding contemporary communities across the globe. However, the heterogeneous structure and variable physicochemical qualities are a key technical impediment to a total transformation in present conversion methods. Under a green biorefinery strategy, an organic-rich portion of MSW might serve as a low-cost, readily accessible substrate for making fuel and high-value chemicals. The present review examines the new issues in municipal solid waste production and management and the generation of diverse bioproducts with added value. In addition, the conversion of organic waste materials into a variety of biofuels, such as liquids, solids, gases, and power, is discussed in this paper. The most up-to-date methods for turning organic waste into high value bioproducts like compost and organic acids are thoroughly examined. The biorefinery technique is bolstered by converting organic solid waste to high value bioproducts that reduce waste, increase energy output, and provide additional healthcare commodities. As a result, it can be said that recycling MSW into high value bioproducts and biofuels will aid in reaching high levels of energy security, environmental protection, and a more robust bioeconomy.

Integration of a drying and pyrolysis system in a green biorefinery: biochar product quality and impacts on the overall energy balance and climate footprint

Green biorefineries can support the reduction of soybeans imports to Europe, by producing protein-rich animal feed from alternative feedstock such as perennial grass and legume species. Once the protein-rich green juice is extracted, a fiber-rich pulp is left as a residue. This work investigates the thermochemical processing of the pulp via pyrolysis as an option to improve the energy balance and climate footprint of a green biorefinery, by producing non-fossil energy and a high-value biochar product. Laboratory-scale pyrolysis and biochar activation were carried out on pulp samples obtained from different perennial species, different pressing method, and maturity at harvest. The results highlighted the importance of the activation stage to obtain a porous biochar, potentially suitable as animal feed additive. The effects on the overall energy balance and climate impact of the system following the integration of pulp drying and pyrolysis, plus a possible activation step for the biochar, were evaluated with a techno-environmental assessment. The pulp sample composition had only limited influence on the climate impact potentials identified. In all cases, it was found that the integration of a combined drying-pyrolysis-activation system in the green biorefinery may provide substantial additional climate benefits but also that the magnitude of these is strongly dependent on the substitution use-value of the energy products.

Non-food crops derived lignocellulose biorefinery for sustainable production of biomaterials, biochemicals and bioenergy: A review on trends and techniques

With advancement in biotechnology and reduction in dependency upon non-renewable refineries, the lignocellulose-based bio-economy has become the part of circular economy. Lignocellulose derived from non-food crops can help to boost the bio-economy when used as a valuable resource in biorefineries for production of various biomaterials, bioenergy and biochemicals for various commercial applications. Non-food crops have always been important in agriculture, supplying fuel, fibre, building materials, and a variety of other valuable resources. This will not only help to stabilise the circular bioeconomy, but it will also help to reduce waste and greenhouse gas pollution. However, there are barriers to using non-food residues in biorefinery in terms of product, innovation, and commercialization. The other major challenge in utilization of plant-based substrate is their complex structure and recalcitrant nature. Thus, advanced biotechnological interventions and policies are required to enhance such biorefineries to produce sustainable bioproducts. This review provides a critical overview on trends and techniques used for the valorisation of non-food crops derived lignocellulose for biomaterials, bioenergy, biochemicals, and other value-added products within the green biorefinery along with critical suggestions on the future potential of non-food crops for environmental sustainability.

Harnessing the Value of Tripolium pannonicum and Crithmum maritimum Halophyte Biomass through Integrated Green Biorefinery.

Bioactive extracts are often the target fractions in bioprospecting, and halophyte plants could provide a potential source of feedstock for high-value applications as a part of integrated biorefineries. Tripolium pannonicum (Jacq.) Dobrocz. (sea aster) and Crithmum maritimum L. (sea fennel) are edible plants suggested for biosaline halophyte-based agriculture. After food production and harvesting of fresh leaves for food, the inedible plant fractions could be utilized to produce extracts rich in bioactive phytochemicals to maximize feedstock application and increase the economic feasibility of biomass processing to bioenergy. This study analyzed fresh juice and extracts from screw-pressed sea aster and sea fennel for their different phenolic compounds and pigment concentrations. Antioxidant and enzyme inhibition activities were also tested in vitro. Extracts from sea aster and sea fennel had phenolic contents up to 45.2 mgGAE/gDM and 64.7 mgGAE/gDM, respectively, and exhibited >70% antioxidant activity in several assays. Ethanol extracts also showed >70% inhibition activity against acetylcholinesterase and >50% inhibition of tyrosinase and α-glucosidase. Therefore, these species can be seen as potential feedstocks for further investigations.

Synergetic Benefits for a Pig Farm and Local Bioeconomy Development from Extended Green Biorefinery Value Chains

As the global population rises, agriculture and industry are under increasing pressure to become more sustainable in meeting this growing demand, while minimizing impacts on global emissions, land use change, and biodiversity. The development of efficient and symbiotic local bioeconomies can help to respond to this challenge by using land, resources, and side streams in efficient ways tailored to the needs of different regions. Green biorefineries offer a unique opportunity for regions with abundant grasslands to use this primary resource more sustainably, providing feed for cows, while also generating feed for monogastric animals, along with the co-production of biomaterials and energy. The current study investigates the impact of a green biorefinery co-product, leaf protein concentrate (LPC), for input to a pig farm, assessing its impact on pig diets, and the extended impact on the bioenergy performance of the pig farm. The study found that LPC replaced soya bean meal at a 50% displacement rate, with pigs showing positive performance in intake and weight gain. Based on laboratory analysis, the resulting pig slurry demonstrated a higher biogas content and 26% higher biomethane potential compared with the control slurry. The findings demonstrate some of the local synergies between agricultural sectors that can be achieved through extended green biorefinery development, and the benefits for local bioeconomy actors.

Recent Trends, Opportunities and Challenges in Sustainable Management of Rice Straw Waste Biomass for Green Biorefinery

Waste rice straw biomass and its burning in open fields have become a serious issue of greenhouse gases emission and air pollution, which has a negative impact on public health and the environment. However, the environmental impact of burning this agro-waste can be mitigated by diverting it towards green biorefinery through the sustainable production of energy, biofuels, organic chemicals, and building blocks for various polymers. This will not only help to reduce the reliance on limited fuels and various chemicals derived from petroleum, but also help in the restoration of the environment in a sustainable manner through its complete utilization. To maximize the inherent conversion potential of rice straw biomass into valuable products, this agriculture waste biomass requires a comprehensive analysis and a techno-economic review for its sustainable management. This review article focuses on the sustainable management of rice straw waste biomass via innovative valorization approaches, as well as the opportunities and challenges encountered in this sector for meeting the demand of current and future green biorefineries.

The effects of grass biomass preservation methods, organic acid treatment and press type on the separation efficiency in the green biorefinery

Processing green biomass into novel products provides opportunities to improve the sustainability of the bioeconomy. The objective of this study was to evaluate the effects of biomass types (fresh, frozen-and-thawed, dried-and-rehydrated and ensiled grass) as well as formic and propionic acid-based additive on the efficiency of liquid-solid separation and crude protein (CP) yield. Three different pressing methods for liquid-solid separation were used. All preservation methods improved biorefinery efficiency compared to fresh grass, and the effect of additive was more profound on the fresh biomass than other materials. However, due to lower CP concentration in the liquid, presumably caused by lower nitrogen solubility, the amount of CP retained in the liquid was not improved in response to the additive treatment. The type of processing technology plays a key role in the extraction of relevant compounds from biomass. With less efficient separation methods, the effects of pretreatments were more pronounced.

Sustainable Management and Valorization of Agri-Food Industrial Wastes and By-Products as Animal Feed: For Ruminants, Non-Ruminants and as Poultry Feed

Substantial increase in the production of agri-food commodities over the past years has resulted in the generation of enormous volumes of wastes and by-products, thus contributing to increased environmental pollution. Being an under-exploited raw material which are rich in bioactive compounds (e.g., polyphenols, dietary fibre, oils, essential vitamins, minerals, etc), novel strategies and initiatives have been proposed and implemented for the effective management and valorization of these wastes and by-products. The proposed initiatives and strategies support the concepts of EU circular economy and green biorefinery, thus promoting sustainability. One of the strategies of management of waste and by-products includes the effectual development of nutritious low-cost sustainable animal feed. Currently, in the world market, there are a range of fruit and vegetable wastes and by-products that have been effectively introduced in animal diets. Within this context, this systematic review focuses on a diversified group of agri-food wastes (and the industrial by-products), their bioactive components, the opportunities for the development of animal feed or feed supplements (for Ruminants, Non-Ruminants and as Poultry feed) and conclusively the health benefits imparted. In addition, the safety issues and regulations aspects are also covered.

Microalgal cultivation on grass juice as a novel process for a green biorefinery

Green biorefineries aim to sustainably produce chemicals, materials, proteins and energy by processing green biomass, such as grass, into a solid fraction (fibers) and a liquid fraction (green juice) for further refining. Here, we propose to incorporate microalgae cultivation in the green biorefinery concept to obtain a higher protein production from green juice obtained from grass. A mixed culture of Chlorella sorokiniana and Acutodesmus obliquus was cultivated on multiple dilutions and after different pre-treatments of green juice from agricultural grass. After 19 days, 1.01 ± 0.06 g/L of algal biomass was reached in a 10 % dilution pre-treated by sedimentation and pH adjustment to 8. Further treatments to reduce the microbial load in the grass juice did not increase algal productivity. The produced biomass had a 41 % protein content, and its heavy metal content and microbial load complied with safety norms for feed, except for yeast and Enterobacteriaceae. Overall, these findings offer new perspectives for protein production in a green biorefinery.