Elsevier

Bioresource Technology

Volume 343, January 2022, 126126
Bioresource Technology

Valorization of agro-industrial wastes for biorefinery process and circular bioeconomy: A critical review

https://doi.org/10.1016/j.biortech.2021.126126Get rights and content

Highlights

  • Valorization of agro-industrial wastes has been comprehensively discussed.

  • Agro-industrial wastes are potential source for value creation.

  • Methodologies for obtaining products from agro-industrial wastes have been appraised.

  • Applications of LCA in agro-industrial circular bioeconomy have been uncovered.

Abstract

Energy recovery from waste resources is a promising approach towards environmental consequences. In the prospect of environmental sustainability, utilization of agro-industrial waste residues as feedstock for biorefinery processes have gained widespread attention. In the agro-industry, various biomasses are exposed to different unit processes for offering value to various agro-industrial waste materials. Agro-industrial wastes can generate a substantial amount of valuable products such as fuels, chemicals, energy, electricity, and by-products. This paper reviews the methodologies for valorization of agro-industrial wastes and their exploitation for generation of renewable energy products. In addition, management of agro-industrial wastes and products from agro-industrial wastes have been elaborated. The waste biorefinery process using agro-industrial wastes does not only offer energy, it also offers environmentally sustainable modes, which address effective management of waste streams. This review aims to highlight the cascading use of biomass from agro-industrial wastes into the systemic approach for economic development.

Introduction

Owing to more industrialization and populace expansion, the generation of waste materials has emerged as a serious issue among researchers (Varjani and Upasani, 2021). As industries counts have been increased, employability, expectancy, land utilization, global trade, etc are few outcomes (Jahnavi et al., 2020, Shah et al., 2021). Major residues are produced by the agro-industries every year. Cereal industries producing husks as waste materials, coffee companies releasing waste in the form of coffee pulp, peels of fruits and vegetables are few examples of agro-industries releasing residues (Cusenza et al., 2021). Energy is required for developing industries and the economy (Yaashikaa et al., 2020). The increase in demand for energy in traditional sources for fulfilling the human requirement resulted in an exploration of all feasible techniques of energy harvesting from various sources (Siwal et al., 2021, Kundariya et al., 2021).

The utilization of agricultural wastes is one technique applied in rural areas for energy production. Bio-based energy is renewable energy obtained from living organisms mainly from agricultural wastes (Anwar et al., 2014, Koyande et al., 2020, Yaashikaa et al., 2019). Wastes from the agricultural sector can be utilized to produce many value-added products such as generating power, biofuel production and generation of biogas (Mohanty et al., 2021). Various substrates possess many properties in them for producing different types of products. Organic compound wastes though toxic to an ecosystem can be used for the production of foodstuffs and other value-added products such as animal feed, biofuels, and biofertilizers (Mishra et al., 2020, Patel et al., 2021). These materials serve as a rich source of minerals, proteins, and sugars. These agricultural residues can’t be termed as wastes rather than labelled as raw materials for the production of value-added products (Usmani et al., 2021). These nutrition-rich materials help in microbial growth also that in turn utilizes these materials.

The disposal and release of these untreated residues into the environment will result in the deposition of contaminants into the ecosystem and finally affecting humans and other living beings (Varjani, 2017, Saravanan et al., 2017, Carolin et al., 2017). These residues or agro-industrial wastes are left either untreated or unutilized hence disposal is being done through dumping into the land, burning, or landfilling. These dumped wastes produce adverse effects on the environment like an increase in temperature, greenhouse gases, etc. For this reason, the development of sustainable management is required. For the exploitation of renewable resources, an integrated form of waste management has to be put forward in the postulation of the circular economy. It is based on the biorefinery idea and the concept of the 3R’s (reduce, reuse and recycle) with the main focus to utilize the raw materials from the agricultural sector (Islam et al., 2021). A new methodology to solve the agricultural issues is the development of an agricultural circular economy. Though the method developed many fields, an efficient strategy is still required for accessing its environmental advantages.

The research in this agricultural circular economy is not completely resolved. LCA (life cycle assessment) is best suited for estimation of impact on the ecosystem at all stages of the agricultural circular economy. This system included the utilization of advanced technologies for reducing wastes using a closed-loop system (Cong and Thomsen, 2021). For efficient progress towards the circular economy, it requires technologies for maintaining the balance between economic and industrial development, protection of the ecosystem with effective utilization of resources.

This review is mainly focused on usage of potential agro-industrial by-products for the production of biobased products under economically feasible and eco-friendly biorefinery process. As of now, there are various ideas of biorefinery process being worked on. The present review comprehensively described possible valorization of agro-industrial wastes and their utilization for generation of renewable energy products. In addition, the review covers various methods of conversion of agro-wastes to value-added products. This paper systematically reviews management of agro-industrial wastes and products from agro-industrial waste valorization for their extensive application(s). Also, application of life cycle assessment (LCA) in agricultural circular bioeconomy has been discussed providing a profound knowledge into where future innovative work should be coordinated towards in order to maximally use biogas and its by-products.

Section snippets

Biorefinery concept and management

The current population size has resulted in maximum utilization of available resources for developing sustainable agricultural practices to lead a defensible life. Hence it is important to set bio-refineries that make use of raw materials mainly biomass, animal, and human wastes (Dragone et al., 2020, Varjani et al., 2020a). Majorly a successful bio-refinery based on energy, food, and chemical production relies on human and government organizations. The product formation depends on the

Sources and effects of agro-industrial waste

Agro-industrial waste refers to materials obtained as wastes from the agricultural field and agriculture-related industries from various processes such as the production of agricultural outcomes such as fruits, meat, vegetables, dairy products, etc. Agricultural wastes can be differentiated as livestock wastes, agro-industrial wastes, crop residues, and fruit and vegetable waste (Zihare et al., 2018; Cusenza et al., 2021). Production of livestock and cultivation of crops facilitates sustenance

Methodologies for valorization of Agro-industrial waste

There are various methods of conversion of agro-wastes to value-added products or energy. Few methodologies include mechanical (Pelletization – a multi-step process for producing energy carrier), thermo-chemical, and bio-chemical are discussed below.

Management of Agro-industrial wastes

Agro-industrial waste management promotes economic advantages like waste conversion to value-added products, cost reduction in the waste treatment process; prevent environmental pollution and other related problems (He et al., 2019). Agro-industrial waste management can be classified into four namely reduction or minimization of waste, conversion, segregation and waste utilization. Waste reduction or minimization is the first type where various steps are to be taken into account including

Products from Agro-industrial wastes

Agro-industry produces a large number of different forms of waste, which mostly came out from waste management processes. The generated waste might be multi-stage and may comprise multi-segment. The possible methods of converting waste materials into useful products using biological principles are investigated.

Application of LCA in agricultural circular bioeconomy

Life cycle assessment has emerged as an important technique for finding eco-friendly and economical outcomes and is mainly aimed at the agro-industrial sector. Major agricultural life cycle assessment analysis was dealt with either anyone concern about the agricultural sector. Studies were very limited on agricultural circular bioeconomy like examining the impact of using waste from the agricultural sector. Various contaminants are also released from different components of the agricultural

Novel methodologies, challenges and future perspectives

There exists a demand for development of novel outcomes and tools for examining and analysing agro-industrial waste valorization in circular bioeconomy. Efforts have been made to generate lignocellulose-based methodologies from agro-waste materials for production of value-added products such as fuels, chemicals, etc (Yaashika et al. 2019; Markande et al., 2021; Prajapati et al., 2021). The production of biofuels and energy from lignocellulosic biomass depends on two primary processes (i)

Conclusions

Agro-industrial wastes have a huge potential to be revalorized for energy generation, and obtaining distinctive bioactive compounds. The reliability between agro-industrial waste management and its operative use is fundamental for fortifying world's economy to circularity. This review pinpointed that agro-industrial waste holds incredible potential to be used as an efficient alternative to fuel derivatives. Agro-industrial waste-based biorefineries are economically feasible as they escalate

CRediT authorship contribution statement

P.R. Yaashikaa: Writing – original draft, Data curation. P. Senthil Kumar: Conceptualization, Supervision, Writing – original draft, Resources. Sunita Varjani: Conceptualization, Supervision, Writing – original draft, Resources.

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

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