Using Central Composite Design to Improve Methane Production from Anaerobic Digestion of Tomato Plant Waste

Abstract

Tomato plant waste (TPW) is a significant agricultural byproduct that has been often underutilized. Recent studies have shown that its use to obtain methane in an anaerobic digestion (AD) process is viable. However, there is not much information available on studies to improve methane production from this substrate using statistical methods for optimization processes such as central composite design (CCD). For this investigation, CCD was adopted to analyze the effect of S/I ratio (substrate/inoculum ratio) (0.32–1.12), temperature (27–43 °C), and inoculum concentration (10.35–20.95 g VS/L) on methane generation and volatile solids (VS) removal in a batch AD system mono-digestion of TPW. The highest average value of methane yield was found to be 210.8 mL CH4/g VS (S/I ratio 0.48, 40 °C, and 18.80 g VS/L), and the highest average value of VS removal was found to be 36.9% (S/I ratio 1.12, 35 °C, and 15.65 g VS/L). We obtain a model with a better fit for the VS removal (R2 = 0.9587) than for the methane production (R2 = 0.9156). Temperature and S/I ratio were the factors most important for methane production and VS removal, respectively.

Bioenergy Generation from Different Types of Waste by Anaerobic Digestion

“…This Special Issue presents papers on many practical and theoretical aspects of waste management in anaerobic biogas production. The papers discuss the conditions and efficiency of the implementation of the processes carried out at laboratory and technical scale, which were aimed at using: (1) lignocellulosic waste from tomato crops in a one-stage vs. two-stage anaerobic digestion process [22,23] (2) biodegradable municipal waste (from households, companies, and gastronomy) collected in a large city [24], (3) confectionery and dairy waste in co-digestion, taking into account the contribution and influence of carrier materials, re-spectively silica/lignin [20] and diatomaceous earth/peat [21], (4) manure, with attention drawn to the positive effects of its storage for several months in a pile [25], (5) burdensome cigarette butts [26], (6) waste from the production of bioethanol for biogas production, as part of an operational hybrid system [18] and (7) corn bran, as a by-product of maize processing, with particular focus on the effects of methods of pressure-thermal agglomeration, as a pretreatment method [27]. Two articles have been dedicated to the management of digestate, discussing its value and applicability in an experimental study on the production of pellets using digestate solid fraction (DSF) [7] and in a review paper [8].…”