September 24, 2022
  • September 24, 2022

How can the textile industry produce more biogas?

By on August 2, 2022 0

A new article in the journal Energies studied the potential for biogas production in the textile industries. Scientists from Brazil and Sweden contributed to the new research.

Study: Comprehensive meta-analysis of pathways to increase biogas production in the textile industryy. Image Credit: Danish Khan/Shutterstock.com

Waste in the textile industry: a critical global environmental problem

The global textile industry produces approximately 92 million tons of waste per year, making it a major polluter. Waste is produced at all stages of the textile manufacturing process. Fiber production, wastewater, solid by-products, transportation, logistics, retail operations, and consumer waste all contribute to this critical issue.

In the textile industry, several thousand chemicals, including dyes, heavy metals, solvents and surfactants, are used to make garments and other products. The presence of these chemicals increases the potential toxicity of discharged solid wastes and effluents, causing environmental damage that can prove harmful for long periods of time.

A major challenge currently facing the industry is the fast fashion trend, which follows a business model of fast manufacturing at low cost and selling cheap items. This model has dramatically increased the waste produced by global apparel and textile manufacturing. While many challenges face the industry today, there is a growing awareness that the textile industry must adapt to the environmental challenges of the 21st century.

Different sources of textile waste used in AD reported in the literature included in the meta-analysis.  TDS = textile dye sludge.

Different sources of textile waste used in AD reported in the literature included in the meta-analysis. TDS = textile dye sludge. Image credit: Anacleto, TH et al., Energies

Sustainable manufacturing

Sustainable manufacturing has become a key goal in many industries and has the potential to significantly mitigate the environmental and health impact of the global textile industry. In recent years, there has been a growing international drive to reduce harm from several industry sectors, including COP 21 and the United Nations Sustainable Development Goals.

These agreements have been an integral part of the reframing of the textile industry. One of the main objectives of governments and international bodies such as the United Nations and the European Union is to significantly improve the circularity of industry, using waste streams to produce value-added products such as biogas and industrial chemicals.

Biogas production

Recently, there has been growing interest in the potential of using textile waste to produce biogas, a key technology in the push towards net zero carbon. Biogas has established itself as a promising energy alternative for the industry and transport sectors.

Anaerobic digestion has been widely applied in several industries to produce biogas and industrial chemicals, while proving to be an environmentally sustainable and inexpensive alternative for waste management. Besides the production of biogas in the textile industry, anaerobic digestion has vast advantages for the treatment and reuse of wastewater.

However, major challenges exist with the efficient production of biogas and other important value-added products in the textile industry using anaerobic digestion alone. Chief among them is the presence of chemicals, recalcitrant compounds and organic pollutants in waste streams. To overcome these challenges, the use of preprocessing has been widely proposed.

Diversity of methods composing the pretreatment categories applied to improve the AD of textile waste reported in the articles included in the meta-analysis.  Biological: alkaline endopeptidase (n=16);  chemical: nutrient (n=4), NaOH (n=1), HCl (n=1), microaeration (n=11), ozonation (n=2), N-methylmorpholine N-oxide (NMMO) (n=1 );  physical: thermal (n=7), autoclave (n=14), sonication (n=3), UV photodegradation (n=1), liquid nitrogen (LN2) (n=4);  chemical + physical: Na2CO3 + thermal (n = 24), thermal + NaOH (n = 1);  chemical + chemical: microaeration + H2SO4 (n = 3).

Diversity of methods composing the pretreatment categories applied to improve the AD of textile waste reported in the articles included in the meta-analysis. Biological: alkaline endopeptidase (n=16); chemical: nutrient (n=4), NaOH (n=1), HCl (n=1), microaeration (n=11), ozonation (n=2), N-methylmorpholine N-oxide (NMMO) (n=1 ); physical: thermal (n=7), autoclave (n=14), sonication (n=3), UV photodegradation (n=1), liquid nitrogen (LN2) (n = 4); chemical + physical: Na2CO3 + thermal (n = 24), thermal + NaOH (n = 1); chemical + chemical: microaeration + H2SO4 (n=3). Image credit: Anacleto, TH et al., Energies

Pre-treatments improve the degradability of organic matter, increase biogas yield and improve the removal of toxic compounds such as dyes. Chemical, biological and physical pretreatment methods can be applied either in isolation or in combination with each other.

Among these methods, biological pre-treatments using microorganisms have been shown to be beneficial due to their cost and energy efficiency, as well as their green credentials due to the absence of harmful chemicals and toxic by-products.

The study

The researchers behind the new paper conducted a systematic review and meta-analysis of current literature and data to assess the effectiveness of pre-treatments for the production of biogas from textile waste. The best choices were identified among the chemical, biological, physical and hybrid pretreatments available. Optimal cost-benefit ratios have been proposed by the authors.

Based on their review of current peer-reviewed literature, the authors revealed that biological pretreatments promote optimal biogas production through anaerobic digestion. An average 360% increase in methane yield is facilitated by enzymatic pretreatment compared to physical and chemical processes.

Additionally, no additional chemicals are required in biological pretreatments, which reduces the number of toxic by-products. This has vast benefits for wastewater treatment and water reuse. Textile industry effluents are cleaner, with lower levels of soluble chemicals and solid waste, reducing environmental and health damage caused by wastewater runoff.

Effect size by natural logarithmic (RR) response ratio of methane yield with 95% confidence interval (CI) (p-value=0.05), comparing the performance of biological, chemical, physical, chemical + physical and chemical + chemical.  Significant code p = 0.05

; n = number of effect sizes per treatment type.

Effect size by natural logarithmic (RR) response ratio of methane yield with 95% confidence interval (CI) (p-value=0.05), comparing the performance of biological, chemical, physical, chemical + physical and chemical + chemical. Significant code p ≤ 0.05

; n = number of effect sizes per treatment type. Image credit: Anacleto, TH et al., Energies

Biological pre-treatments also possess a favorable cost-benefit ratio, with low investment cost and low energy consumption thanks to these processes for treating textile waste before anaerobic digestion and biogas production.

Implementing these processes in the textile industry offers huge benefits for reducing harmful waste and using waste streams to produce value-added products such as biogas. This improves the circularity of the global industry, helping it achieve its sustainability goals. However, while there are vast benefits, further research into new enzymes and wastewater treatment is needed if this solution is to be fully realized in the future. Further reading Anacleto, TH et al. (2022) Comprehensive meta-analysis of pathways to increase biogas production in the textile industry [online] Energies

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