The Effects of Using Pretreated Cotton Gin Trash on the Production of Biogas from Anaerobic Co-Digestion with Cow Manure and Sludge

Muhammad Usman Hanif,Muhammad Adnan Hanif,Ali Bahadar,Mohammed Zwawi,Nazia Hossain,Adeel Waqas,Sergio C Capareda,Muhammad Tahir Hussain Siddiqui,Hamid Iqbal,Mohammed Algarni,Asma Jamil,Sabzoi Nizamuddin

doi:10.3390/en15020490

Abstract

Anaerobic co-digestion (AcoD) has been practiced for decades to convert waste into value-added energy products, especially biogas. This study aimed to assess the potential of biogenic methane (CH4) production from the co-digestion of pretreated cotton gin trash (CGT), cow manure, and sludge. CGT contains high cellulosic content, making it a reliable feedstock for biogenic methane production. To further improve the biogas quantity and quality, the CGT was subjected to physical pretreatments, i.e., hot water (HW), ultra-sonication (US), and a combination of both (HW+US). After 91 days of AcoD, 79–110 L of biogas was produced by the treatments. Among the treatments, HW+US-pretreated CGT presented maximum biogas production capacity, at 110 L. Besides, this treatment showed the high-quality biogenic CH4 content, 52.4% of the total biogas volume, with an improved conversion rate of 0.37 L/g of volatile suspended solids consumed. In addition, this study discussed the structural changes in feedstock due to pretreatments and correlated them with the corresponding biogenic methane production. The study reports the potential of pretreated CGT conversion to CH4. It will impact the circular economy by contributing to on-farm energy requirements and reducing the financial expenditures incurred in this regard.

Highlights

Co-digestion is a well-established and conventional method where a combination of different feedstock is processed into the fundamental anaerobic digestion technique to increase the biogenic methane content of produced biogas [1]
The fresh samples of cotton gin trash (CGT), cattle manure (CM), and inoculum sludge were obtained from Varisco cotton gin near College Station, in Brazos County, Texas, animal science (ASTREC) facility at Texas A&M University, and the recycling stream of the anaerobic digester in the Texas A&M for sewage sludge, respectively
The sludge had high nitrogen content but minimal volatile suspended solids (VSS). These results suggested that the sludge was stabilized, and it carried out the minimal microbial activity within its mass

Summary

Introduction

Co-digestion is a well-established and conventional method where a combination of different feedstock is processed into the fundamental anaerobic digestion technique to increase the biogenic methane content of produced biogas [1]. During the last two decades, a wide variety of biomass has been co-digested for bioenergy production Among this common biomass, a few remarkable feedstocks have been reported as a promising output for methane production, such as cotton wastes [2], organic solid waste [3], sewage sludge [4], rice straw [5], and microalgae [6]. Lay et al [7] reported that 1 g of sludge, meat, and vegetables produced 450, 424, and 203 to 269 mL of methane (CH4 ), respectively This result suggests that the plant-based recalcitrant material has less methane production capacity than the protein-based and stabilized biomass. This consequence can occur due to the high nitrogen content and resulting carbon to nitrogen ratios [7]

Objectives

Methods

Results