Is cellulase production by solid-state fermentation economically attractive for the second generation ethanol production?

Abstract

The cost of enzymes for the enzymatic route of the second generation ethanol production is a crucial bottleneck to turn this process into a reality. Solid-state fermentation (SSF) is an environmentally friendly process of enzyme synthesis, although little is known about the costs associated to it. Therefore, this work analyzed economical scenarios of cellulase production by SSF in a pilot plant integrated to both a first and a second generation ethanol processes. The chosen substrate for the enzyme production was composed by sugarcane bagasse and wheat bran, cultivated by the thermophilic fungus Myceliophthora thermophila I-1D3b at 45 C during 96 h. The estimation of the most important economic indicators showed that the SSF process is economically attractive, due to its easy integration to the main process, and its revenue is up to four fold greater than electricity cogeneration. Economic indicators, such as the internal rate of return (IRR) and payback, were higher than those usually accepted by Brazilian investor in the sucro-energetic sector. Nevertheless, return on investment (ROI) was under than that recommended by the literature. The sensitivity analysis showed strong influence of the enzyme activity on the economic indicators, being the most important parameter for the project profitability.

Brazilian agricultural and livestock substrates used in co‐digestion for energy purposes: Composition analysis and valuation aspects

“…The sugarcane bagasse, now so-called a co-product, has its opportunity cost as a source to produce bioelectricity and its value reaches US$ 10-15 a ton. 69 However, while this study was carried out, no reasonable value for vinasse, the most recommended co-product for AD, could be identified in the scientific literature. The distilleries still regard it as an effluent (a by-product), simply focusing on its chemical properties for soil nutrition, particularly potassium replacement.…”

“…This debate is crucial to enable material exchange, especially in SPS, where the citrus and sugarcane belts are adjacent. The sugarcane bagasse, now so‐called a co‐product, has its opportunity cost as a source to produce bioelectricity and its value reaches US$ 10–15 a ton 69 …”

Structured Polyvinyl Alcohol/Zeolite/Carbon Composites Prepared Using Supercritical Fluid Extraction Techniques as Adsorbent for Bioethanol Dehydration

“…On the other hand, alternative renewable fuels provide eco-friendly, inexpensive, and pollution-free options that increase energy security [2]. In this case, bioethanol production is becoming more attractive for the scientific community [3]. Currently, bioethanol production has increased by 4,959 kilotons in 2007, to 97,280 kilotons in 2017, which significantly contributes to the wholesale of biofuels in the world with a value of approximately 58 billion dollars per year [4,5].…”

Pretreatments of Carnauba (Copernicia prunifera) straw residue for production of cellulolytic enzymes by Trichorderma reesei CCT-2768 by solid state fermentation

“…However, the production of cellulosic ethanol requires fermentation of sugars derived from the hydrolysis of lignocellulosic biomass by the action of enzymes such as cellulases and xylanases [4]. Lignocellulolitic enzymes play an important role in the bioconversion of lignocellulosic biomass; nevertheless, the production cost of these enzymes has been an obstacle in industrial production and bioprocesses [5,6]. Hence, there is a focus on identifying microorganisms that secrete these enzymes with higher efficiency and cheaper carbon sources [7,8].…”