Waste and Biodiesel: Feedstocks and Precursors for Catalysts

By Bhaskar Singh

Waste and Biodiesel: Feedstocks and Precursors for Catalysts is a comprehensive reference on waste material utilization at various stages of the biodiesel production process. The book discusses the technologies for converting cooking oil and waste animal fats to biodiesel, along with the efficacy of municipal waste derived lipids in biodiesel production. The use of wastewater-grown microalgae feedstock, oleaginous fungi, bacteria and yeast produced using waste substrate are also discussed. The use of various catalysts is addressed, including CaO derived from waste shell materials, fish and animal waste, inorganic waste materials like red mud and cement waste, and whole cell enzymes using waste substrate.

Each chapter addresses the challenges of high production costs at a pilot and industrial scale, offering methods of cost reduction and waste remediation. This book is a valuable resource for researchers and industry professionals in environmental science, energy and renewable energy.

• Provides a comprehensive assessment of waste for biodiesel production, including novel feedstocks such as waste cooking oil, animal fats and municipal waste
• Discusses the synthesis of cost-effective catalysts from various waste materials such as animal bones, fish scales, shells, red mud and cement waste
• Presents multiple methods of cost reduction in biodiesel production, e.g., by utilizing waste as a nutrient source for oleaginous algae and fungi

• Language: English
• Publisher: Elsevier Science
• Release date: Feb 28, 2022
• ISBN: 9780128242315

Book preview

Chapter 1

Biodiesel and an overview of waste utilization at the various production stages

Shahrukh N. Alama, Zaira Khalida, Abhishek Guldheb, Bhaskar Singha

aDepartment of Environmental Sciences, Central University of Jharkhand, Ranchi, India

bAmity Institute of Biotechnology, Amity University Maharashtra, Mumbai, India

Abstract

Cost effective production is requisite for biodiesel production to realize its potential as alternative renewable fuel. Conventional feedstocks and catalysts used for conversion are the major contributors towards the production cost of biodiesel. The cost of production can be reduced by integration of waste material as a feedstock, utilization of waste for generation of feedstock and using inexpensive waste derived catalysts in the process. Recently researchers are identifying potential waste materials and developing strategies for incorporation in biodiesel production process. Waste feedstocks such as waste cooking oil and animal fats are gaining popularity. Promising feedstocks such as microalgae and oleaginous fungi can be cultivated using waste streams and material. Several waste materials such as animal bones, egg shells and plant residues have been studied for synthesis of catalysts used in transesterification reaction. These strategies not only make biodiesel production process economical but also offer environmental benefits in terms of waste utilization and management.

Keywords

Biodiesel; Waste; Wastewater; Feedstock; Catalyst

1.1 Introduction

Fossil fuel reserves throughout the world are declining at an exponential rate mainly attributed to population explosion. Above all, the extensive burning of fossil fuels for transportation, energy, industrial application creates negative environmental issues, such as global warming, continuous CO2 emission, and green house gas emission. Global energy consumption has already doubled between 1971 and 2001 and it is estimated that energy demand by 2030 is to be called for additional increase by 53%. Since, the fossil fuels are nonrenewable and as per British Petroleum's (BP) annual report, 2013 it will get exhausted in around 50 years if the current pace continues. Consequently, sustainable fuel alternatives are becoming a high priority for many countries and are bound to play a major role in the fuel industry in the immediate future. Liquid biofuels are being advocated as one of the most sustainable alternatives to deal with ever-increasing demand and to tackle environmental concerns, including diminishing fossil fuel reserves and global warming. Biodiesel has been identified as one of the best alternative nonpetroleum based sustainable fuel consisting of alkyl esters derived from either the the esterification of free fatty acids (FFAs) or transesterification of triglycerides (TGs) or with short-chained alcohols. Production of biodiesel from biological renewable sources, such as vegetable oils, animal fats, waste oils and recently lignocellulosic materials are being reviewed widely. Many advantages of biodiesel over conventional petroleum diesel are: it has low emissions and hence safer, renewable, biodegradable, better lubricity, nontoxic, it contains no sulfur and biodegradable. Biodiesel is the only alternative fuel to complete the health effects test requirements of the Clean Air Act Amendments 1990. Currently, it is not among the popular alternative fuel globally mainly because of its higher cost when compared with conventional petroleum diesel. The major problem in the widespread commercialization of biodiesel is the availability of the feedstock, which makes the cost of production a bit high, thereby raising the overall price. However, the recent advancements in using the cheap raw material instead of pricy refined vegetable oil and fat is showing promising results in making biodiesel more economical.

This chapter addresses an overview of utilization of various waste materials, such as waste cooking oil, waste animal fats, agricultural wastes, waste coffee grounds, etc., and the challenges and other prospects of using these wastes material.

1.2 Biodiesel production process

The direct use of any kind of vegetable oil or fat or its blend for the purpose of running an engine has been deemed impractical, mainly due to its characteristics like high viscosity, free fatty acid content and acid composition of such oils. These types of oils and fats also have the problem of gum formation because of polymerization and oxidation while storing and combusting. Additionally, thickening of unprocessed oil with time and deposition of carbon are two more issues which make it unfit for direct application (Fukuda et al., 2001). Keeping in view, the problems mentioned the oils and fats needs to undergo conversion processes to make or convert them into viable biodiesel form suitable for conventional diesel engine. Transesterification of vegetable oils or fats with alcohol (with one to eight carbon atoms) is the most widely adapted and preferred method for biodiesel production. Basically, there are two transesterification methods, one is performed with catalyst and the other is performed any without catalyst. The utilization and selection of type of catalyst is depended on type of the feedstock. Generally the use of catalysts improves the rate and yield of biodiesel and is preferred over the other depending on the feedstock being used for producing biodiesel. According to Otera (1993) transesterification reaction can be defined by three reversible reactions where excess alcohol shifts the whole equilibrium to the product side as depicted in Fig. 1.1.

Figure 1.1 Transesterification reversible reaction.

First step involves the reversible reaction of changing of triglycerides to diglycerides, then the second reaction is changing of diglycerides to monoglycerides, similarly followed by conversion of monoglycerides to glycerol. All the reactions yield one molecule of methyl ester per mole of glyceride at every step (Noureddini et al., 1998). Sometimes, esterification prior to the transesterification process is the most common method for reducing the feedstock's free fatty acid (FFA) content.

The complete reaction involved in transesterification process is:

As depicted in Fig. 1.2, R1, R2, and R3 are long chains of hydrocarbons and carbon atoms called fatty acid chains, which may be same or different with CH3 and C2H5 attached. The transesterification reaction is based on one mole of triglyceride reacting with three moles of methanol to produce three moles methyl ester (biodiesel) and one mole glycerol.

Figure 1.2 Transesterification process depicting methanolysis of triglyceride.

Several kinds of alcohols can be incorporated in this reaction, such as ethanol, butanol, propanol, or methanol. However, methanol is most commonly used based on the low-cost, several physicochemical benefits (high polarity and shortest alcohol chain (Ma and Hanna, 1999).

The transesterification reaction involves few important parameters which significantly impacts the final yield. Some of the most important variables are: reaction time, free fatty acid content in the oil, reaction temperature, water content in the oil, type and amount of catalyst, molar ratio of alcohol to oil, use of cosolvent and mixing intensity.

1.3 Integration of waste into biodiesel production process

Current biodiesel industry mostly employs edible oilseed as feedstock and strong base and acid based homogenous catalyst mainly due to high conversion rates. However, high costs of these type of feedstocks, catalyst, and other expensive process, such as purification of final product or separation of catalyst makes the whole cost of biodiesel expensive and impractical (Santosa et al., 2019). In order to reduce the production cost, research involving the incorporation of waste materials in several biodiesel production stages is being favored. There are various advantages in utilizing or reusing the waste materials with disposal and recycle issues. Instead of just throwing away the waste materials where it may damage the environment, utilizing it in biodiesel solves multiple problems including employment generation for a large number people in waste recovery and production stages.

Waste materials have been incorporated in various biodiesel production stages viz. as feedstock for biodiesel production or using heterogeneous catalyst derived from several waste materials instead of homogenous catalyst. The heterogeneous catalyst have several economical and environmental advantages in addition to low production cost, such as it can be easily separated at the end of the biodiesel production processes by centrifugation or filtration and also they can be reused several times (Gotcht et al., 2009). These heterogeneous catalysts are much safer to handle, less corrosive, and more eco-friendly (Lam et al., 2010). Recent studies show several kinds of wastes ranging from lignocellulosic wastes, shell wastes, and others have been successfully used as catalyst for biodiesel production. Including various types of CaCO3 based wastes as catalyst, such as waste egg shell (Bharti et al., 2020), waste shell (Yuliana et al., 2020), waste fish scales (Chakraborty et al., 2011), waste animal bones (Farooq et al., 2015), waste coral fragment (Roschat et al., 2012), and others. Similarly various lignocellulosic biomass has also been investigated for low cost catalyst such as sugarcane baggase (Akinfalabi et al., 2020), rice husk ash (Hindryawati et al., 2014), bamboo (Zhou et al., 2016), palm shell (Baroutian et al., 2010), etc.

Several wastes utilized as biodiesel feedstock like waste oil, animal fat, agricultural waste, municipal waste, lignocellulosic waste, etc., have been discussed in detail below.

1.4 Waste material as feedstock

The increased energy demand, growing concern for the environment and the possible shortage of petroleum fuels in future have incentivized the research toward finding alternative sustainable fuel (Pagliano et al., 2017). Biodiesel has come forward as a promising alternative to petroleum fuel with similar physicochemical properties as diesel that can be used as its substitute in diesel engines without any need for modification (Mardhiah et al., 2017). Biodiesel is most commonly synthesized from oilseeds which strongly influence the global food security while increasing the price of edible oils thereby shifting the focus towards non-edible as well as waste cooking oil (Patil et al., 2011). The incorporation of municipal, domestic, and agroindustrial waste feedstock for biodiesel production makes the process sustainable and eco-friendly (Aboelazayem et al., 2018).

1.4.1 Waste oil

Biodiesel are ethyl or methyl esters extracted from different feedstocks through the process of transesterification (Sharma et al., 2013). The availability of waste feedstock creates an attractive option of overcoming the energy crisis by conversion of these feedstocks to biofuel. Waste cooking oil (WCO) presents itself as a promising biofuel feedstock since it is a waste that is readily available from household kitchens, restaurants, and cafeterias. The utilization of waste materials for biodiesel production will be helpful in mitigation of pollution. WCO which is generally disposed off as waste can be exploited as a feedstock making the whole process economical (Arshad et al., 2018; Tangy et al., 2016). The production of biodiesel from WCO is deemed to be cost effective, technically viable and environmentally benign (Farooq et al., 2013). It is estimated that United States of America, Japan, China, Europe, and Malaysia together accounts for 15 million tonnes of WCO generation per year on an average. India is one of the largest producers of WCO with an estimate of 9.2 million tons per annum (Bharti et al., 2020; Kolhe et al., 2017). Che et al., (2012) used olive pomace oil for the production of fatty acid methyl ester (FAME) via acid esterification process with sulfuric acid as catalyst. Reduction in free fatty acid (FFA) by 50% at low methanol to oil ratio while for high methanol to oil ratio over 80% reduction was observed. Furthermore, Ouachab and Tsoutsos (2013) also used olive pomace oil for the production of FAME through esterification process achieving a yield of 97.8% (Table 1.1).

Table 1.1

The process of transesterification has eliminated durability and operational problems while reducing the viscosity of vegetable oil. Biodiesel blend of WCO in performance characteristics are close to diesel fuel (Abed et al., 2018). Mohod et al. (2013) in their study compared B5 and B10 blends of WCO biodiesel with diesel fuel by using it in a single cylinder diesel engine. The biodiesel blend resulted in reduction of thermal efficiency by 2.8% and increase in specific fuel consumption by 4%. Muralidharan and Vasudevan (2011) tested four blends of diesel-WCO biodiesel; diesel fuel, B5, B20, and B30 in diesel engine and found higher fuel consumption load in biodiesel blends since heating value of biodiesel is lower when compared with diesel fuel. The WCO biodiesel fuel synthesized by transesterification process is similar to diesel fuel in its physical and chemical properties. The ongoing studies focus on the functioning of biodiesel blend of WCO with diesel fuel in the operation of diesel engine without any alteration in hardware (Abed et al., 2018).

1.4.2 Waste animal fats

Meat processing facilities produce animal fats as a by-product. Recently a lot of attention is paid on the economically sustainable feedstock, animal fat waste (AFW) being one of them (Habib et al., 2020). The animal fat derived from the meat processing facility mainly include white grease and lard from pork, tallows from cattle, poultry fat from turkey, chickens, ducks, and other birds. Oils and fats derived from leather industry waste and fish processing plants are also deemed to be a viable feedstock for biodiesel (Alptekin et al., 2012). Currently, animal fat for the most part is used as raw material in soap and cosmetics industries making the market demand for AFW very limited. AFW offers environmental, economic as well as food security benefit over the conventional edible vegetable oils when used as a feedstock for biodiesel. Additionally, the cost for transesterification of AFW i.e., $0.4-0.5/liter is cheaper than the transesterification cost of vegetable oil which is $0.6–0.8/liter (Banković-Ilić et al., 2014). Some AFW, such as chicken, tallow, lard fats are already in use for biodiesel production at industrial scale (Bender, 1999; Schörken and Kempers, 2009). AFWs require complex techniques for biodiesel production since they contain high levels of free fatty acids (FFA) and saturated fatty acids which results in lower chemical and physical quality of biodiesel. Despite that, AFW's low unsaturation of fatty acids has numerous advantages, such as high cetane number, high calorific value, and high oxidation stability (Alptekin et al., 2012). Since, AFW contains high quantity of FFA and water resulting in reduced yield of biodiesel as well as increased production cost, pretreatment is essential which alleviates the problem of separation and purification (Gebremariam and Marchetti, 2018). The production of biodiesel takes place through the process of transesterification which involves reaction of fat in the presence of a catalyst with short chain alcohol. There are many catalysts available for use in the production of biodiesel (Toldrá-Reig et al., 2020). Catalysts, such as potassium hydroxide, potassium amide, potassium methoxide, potassium hydride, sodium hydroxide, sodium amide, sodium methoxide, sodium hydride, sulfuric acid, phosphoric acid, hydrochloric acid, organic sulfonic acid, lipase, zirconias, silicates, and nanocatalysts, are some of the most widely used alkali, acidic, generous, and complex catalysts used in transesterification reaction (Ma and Hanna, 1999). The use of alkali catalyst in AFW transesterification results in a faster reaction rate (4000 times faster) in comparison with acid catalysts. The other benefit of using alkali catalysts is that it is readily available and less expensive. Various studies have been conducted using AFW for the production of biodiesel, few of which are mentioned in Table 1.2.

Table 1.2

1.4.3 Agricultural waste

Agricultural crop residues or agricultural wastes can be broadly classified into two types:

1. Field residues: Materials which are left in plantation areas or agricultural land after harvesting. Field residues generally include stalks, rice bran, stems, seed pods, etc.

2. Process residues: The leftover materials after the crop is processed to some usable resource are called process residues. These process residues may include husks, roots, bagasse, seeds, and deoiled cakes of edible and nonedible oil