Incorporating biowaste into circular bioeconomy: A critical review of current trend and scaling up feasibility

doi:10.1016/j.eti.2020.101034

Environmental Technology & Innovation

Volume 19, August 2020, 101034

https://doi.org/10.1016/j.eti.2020.101034 Get rights and content

Highlights

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Thermochemical and biochemical conversion processes are reviewed.
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Bioenergy, biochar and other biowaste products are useful in industry application.
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Technical constraint with wet biowaste could be overcome by process optimisation.
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Co-production and exploration of new strain can improve up-scaling feasibility.
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Sustainable cultivation of energy crop helps in carbon sequestration.

Abstract

Valorisation of biowaste is a topic of closer scrutiny for its role in transition of fossil-based economy to bioeconomy. Increasing waste generation and climate change are among the issues that can be alleviated via biowaste valorisation. Various conversion methods have been consolidated as the most effective methods to valorise biowaste into value-added products such as biofuel, biochar and other biomaterials. Recognising the need to identify areas with higher demand for scientific effort, this review aims to provide a critical overview on current trend pertaining biowaste valorisation. The rheological limitations that hinder the upscaling feasibility of biowaste valorisation are provided and discussed. Survey of academic literature to showcase the recent efforts to alleviate technical constraints is also included. With critical approach, this review is expected to highlight the setbacks and avenues in biowaste valorisation field that are useful for future research. Specifically, process optimisation and development of new products with competitive edge from biowaste are the key avenues to close the loop of circular bioeconomy.

Introduction

Our mother nature provides abundant biomass (170 billion tonnes annually), which is also the only replenishable carbon source on earth that can be transformed into solid, liquid hydrocarbon and gas (Yang et al., 2018). However, only 3.5% wt, approximately 6 billion tonnes of the biomass are used by human (Röper, 2002). Annually, nearly 1.3 billion tonnes of biowaste is thrown away (Bhatia et al., 2018), which result in high energetic and monetary cost for the government to properly manage disposal of biowaste. Hence, it is imperative for us to understand that biomass is misplaced asset that offers promising options as sustainable fuel and value-added products, rather than as biowaste that needs to be disposed.

The major issue which sparked the interest in valorisation of biowaste is global warming. Ever since industrial revolution, fossil fuel is widely used to power anthropogenic activities such as transportation, power generation, industry, agriculture and mining (Gutknecht et al., 2018). This conventional energy source is anticipated to deplete in the next 40–50 years. To abate the problem, a paradigm shift in energy use from conventional fossil fuel to renewable bioenergy is needed. In fact, in year 2011, bioenergy is ranked as the top four energy sources in the world final energy consumption (Saidur et al., 2011), which contributes to 14% of the total energy accounted.

Valorisation of biowaste into bioenergy offers several advantages. Firstly, biowaste that is easily combustible can be utilised as energy source without modification. Secondly, bioenergy is carbon neutral fuel (Sikarwar et al., 2016). Incorporating biowaste as feedstock for bioenergy not only reduces the carbon footprint but also has fewer problems with storage compared to other renewable energy such as solar or wind. Bioenergy is also replenishable and abundant in nature (Shen et al., 2020). In addition, bioenergy is versatile because biowaste can be valorised into biogas, biochar, liquid hydrocarbons or electricity (Saidur et al., 2011).

Recognising the important role biowastes have in the economies, it is reasonable to ask if the valorisation of biowaste can be powered in a way that supports circular bioeconomy. Therefore, this article provides a broad overview of current trends in biowaste valorisation and identifies the underlying theoretical drawbacks that hinder upscaling of the technology. Possible avenues and progress made in the field are also explored to discuss the potential to improve technical, economic and environmental feasibility of biowaste valorisation.

Section snippets

Conversion processes into value-added product

Biowaste commonly constitutes of different amount of cellulose, hemicellulose, lignin, lipids, protein, and carbohydrates. Among these, the major compounds in biowaste are cellulose, hemicellulose and lignin which are also termed as “lignocellulose” (Chen et al., 2015b). Cellulose and hemicellulose are sugar compounds that make up macromolecules while lignin is made of aromatic polymers (Saidur et al., 2011).

Although some biowaste can be combusted directly to be used as fuel, the combustion

Overview

The reliance of global economic activities on fossil fuel has depleted the storage of fossil fuel in a rapid manner. In fact, population growth represents more energy demand to be met to power economic activities in developing countries (Ragauskas et al., 2006). However, the dependence of fossil fuel should be reduced because combustion of fossil fuel release greenhouse gases and lead to global warming. Statistically, the temperature between 2015 to 2019 has been regarded as the

Setbacks and avenues

Declining fossil fuel supply, problem with energy security, environmental concerns and sustainability issue has prompt the valorisation of biowaste into bioenergy or other value-added products. Though biowaste is a prominent option to abate the aforementioned issue, there are still many setbacks to be identified and addressed before biowaste valorisation can be up-scaled to wider application.

Concluding remarks and future prospect

As with any scientific progress, the development of valorisation of biowaste would not be without difficulties. To achieve the status of bioeconomy (as shown in Fig. 2), the economic environment needs to integrate biowaste into multiple aspects. However, systematic analysis and critical review of setbacks and avenues would open up the opportunity and impetus for technological advancement especially in research and development area (R&D). The use of biowaste as feedstock for producing

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.

Acknowledgements

The author is grateful for the help of Kyan in graphic illustration.

Funding

The authors acknowledge the funding provided by University of Malaya, Malaysia under SATU Joint Research Scheme [ST014-2018, ST022-2019] and Impact Oriented Interdisciplinary Research Grant, Malaysia [IIRG004A-19IISS] as well as [RP025B-SUS18]. The authors are also grateful for funding from Ministry of Higher Education, Malaysia for Fundamental Research Grant Scheme [FRGS/1/2019/STG05/UNIM/02/2] and MyPAIR-PHC-Hibiscus Grant,

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Incorporating biowaste into circular bioeconomy: A critical review of current trend and scaling up feasibility

Highlights

Abstract

Introduction

Section snippets

Conversion processes into value-added product

Overview

Setbacks and avenues

Concluding remarks and future prospect

Declaration of Competing Interest

Acknowledgements

Funding

Renew. Sustain. Energy Rev.

Renew. Sustain. Energy Rev.

Environ. Technol. Innov.

Biomass Bioenergy

Bioresour. Technol.

Energy Sustain. Dev.

Energy Convers. Manage.

Energy Convers. Manage.

Prog. Energy Combust. Sci.

Waste Manage.

Appl. Energy

Fuel

Fuel

Energy

Bioresour. Technol.

Renew. Sustain. Energy Rev.

Renew. Sustain. Energy Rev.

Bioresour. Technol.

Bioresour. Technol.

Prog. Energy Combust. Sci.

Chem. Eng. J.

Bioresour. Technol.

Bioresour. Technol.

Renew. Energy

Energy Procedia

Proc. Combust. Inst.

Chem. Eng. J.

Renew. Sustain. Energy Rev.

Appl. Energy

Renew. Sustain. Energy Rev.

Bioresour. Technol.

Curr. Opin. Chem. Eng.

Energy Procedia

Fuel Process. Technol.

Bioresour. Technol.

Bioresour. Technol.

Energy Convers. Manage.

Chemosphere

Agricult. Ecosys. Environ.

Energy Sustain. Dev.

Electrochim. Acta

Appl. Energy

Renew. Sustain. Energy Rev.

Appl. Energy

J. Electroanal. Chem

Bioresour. Technol.

Renew. Sustain. Energy Rev.

Renew. Sustain. Energy Rev.

Appl. Energy

Sci. Total Environ.