Volume 5 biomass and biofuel production 5 20 – biomass to chemicals Volume 5 biomass and biofuel production 5 20 – biomass to chemicals Volume 5 biomass and biofuel production 5 20 – biomass to chemicals Volume 5 biomass and biofuel production 5 20 – biomass to chemicals
5.20 Biomass to Chemicals A Kazmi and J Clark, University of York, York, UK © 2012 Elsevier Ltd All rights reserved 5.20.1 5.20.2 5.20.2.1 5.20.2.2 5.20.2.3 5.20.2.3.1 5.20.2.3.2 5.20.2.4 5.20.2.4.1 5.20.2.4.2 5.20.2.4.3 5.20.3 5.20.3.1 5.20.3.1.1 5.20.3.1.2 5.20.3.2 5.20.3.2.1 5.20.3.2.2 5.20.4 5.20.4.1 5.20.4.2 5.20.4.3 5.20.4.4 5.20.5 5.20.5.1 5.20.5.2 5.20.5.3 5.20.6 References Introduction Biodiesel: Conversion of Glycerine Coproduct and Other Side Streams Introduction Biodiesel Production without the By-Product Glycerol Increasing the Value of Glycerol Purification of crude glycerol Current uses of glycerol Chemicals from Glycerol Recent reviews Example 1: Citric acid Example 2: Propylene glycol Fuels from Fermentation Processes: Use of Biomass Raw Material, Fuel Production Intermediates, and Coproducts for Chemical Production Lignocellulosic Feedstocks for Chemical Production Converting cellulose to sugars Sugars to chemicals Lignin: Depolymerization or Direct Use? The disassembly of lignin Uses of lignin Use of Bio-Alcohols as Chemicals and Chemical Intermediates Ethyl Acetate Single-Walled Carbon Nanotubes Hydrogen Ethanol Fuel Cells Biochar (Solid Biofuel): Chemicals from Pyrolysis Oil Comparison of Major Techniques Polycyclic Aromatic Hydrocarbons Fabricated Microwave Pyrolysis Conclusions and Future Prospects Glossary Bioethanol Ethanol derived from biomass and used as fuel Biomass Any material which has been or is alive In this field of biorefineries, biomass normally refers to agricultural materials Biorefinery A concept which involves using biomass as a feedback to produce chemicals, materials and energy using various processes 395 396 396 396 396 396 397 398 398 399 399 400 400 400 400 401 401 404 404 405 405 406 406 406 406 407 407 408 409 Fermentation A process involving a micro-organism which converts an organic material into other chemicals Green chemistry Chemistry using sustainable and environmentally friendly processes and materials Pyrolysis The breakdown of chemical structures using an energy source in the absence of oxygen 5.20.1 Introduction Humans have relied on fuel since the beginning of civilization, unlike any other creature in this world It was very fortunate that early human beings had an abundant source of fuel in the form of wood, which was used for many millennia to propagate society As this resource dwindled, humans searched for fuel underneath the earth, and the discovery of fossil fuels not only provided a colossal amount of fuel, but also an abundant source of chemicals, which the society would use to nourish its demand for a growing population and an increasing standard of living However, in the process of manufacturing chemicals, industry has relied on nonrenewable resources and low-efficiency and highly wasteful methods The broad focus of the principles of green chemistry is to avoid using such conventional methods and reduce the environmental impact for a sustainable future A major problem the world currently faces is the disposal of waste, and the green chemistry vision primarily is that waste generation should be prevented and if not possible then valorization methods should Comprehensive Renewable Energy, Volume doi:10.1016/B978-0-08-087872-0.00526-6 395 396 Expanding the Envelope be implemented One method of reducing waste is to incorporate all materials used into a final usable product In any chemical reaction or processing technology, the energy requirements should be rationalized and minimized Energy costs have always been accounted for in financial balance sheets; however, it will not be long before CO2 is accounted for in life cycle analysis (LCA) of processes and products Optimizing reactions and processes to work at ambient temperature and pressure would decrease the environmental impact In many cases, the environmental impact over the life cycle can be further improved if the feedstock is a renewable resource and the final product biodegradable This chapter considers chemical production from biodiesel by-products and then moves on to the production of chemicals from lignocellulosic materials derived from bioethanol supply chains and elsewhere Additional opportunities are then explored by considering the use of bioethanol as a commodity chemical feedstock, a specialty chemical feedstock, and an electrochemical feedstock The chapter concludes by looking at the prospects for recovering useful chemical feedstocks from the products produced when biomass is pyrolyzed 5.20.2 Biodiesel: Conversion of Glycerine Coproduct and Other Side Streams 5.20.2.1 Introduction The transesterification of triglycerides produces three molecules of fatty acid methyl esters (FAMEs) and a molecule of glycerol FAME is also known as biodiesel and can be used in conventional diesel engines Triglycerides are found in natural oils such as palm, rapeseed, or sunflower oil and in animal fat A large industry has now developed that uses such resources to manufacture diesel and according to the ‘IEA task 38’ report Germany is the world’s largest producer with a 29% share, which equates to 3.2 billion liters per annum worldwide [1] The biodiesel market is highly dependent on the price of mineral diesel and therefore low crude oil prices can make mineral diesel so cheap that biodiesel is no longer economically viable Furthermore, the production of biodiesel is not very efficient and green because the final mixture requires being separated and washed several times to meet fuel standards Waste products such as salts add to the glycerol waste, making disposal a significant cost to the company Therefore, it is important to utilize such materials and instead of being a cost, they could generate income for a company Pure glycerol itself can be sold to various industries and any derivatization to produce value-added products could significantly enhance the economics However, if novel routes to biodiesel are developed that yield no glycerol by-products, then many of the above issues would be resolved 5.20.2.2 Biodiesel Production without the By-Product Glycerol Notari and Rivetti [2] have shown that biofuels can be produced without glycerol by using dimethyl carbonate as a reactant The transesterification of triglycerides with dimethyl carbonate [3–5] produces a mixture of three molecules of FAMEs and one molecule of glycerol carbonate, which is suitable for use in diesel engines The use of enzyme technology, which can be expensive, to produce biodiesel has become popular due to its more environmentally friendly credentials and has also been used to produce biodiesel without any glycerol by-product Using lipases, triglycerides can be converted to three molecules of esters plus one molecule of monoglyceride (MG) [6] or glycerol triacetate [7] All of these processes are still at the research stage and no significant commercial developments have taken place Therefore, currently and in the foreseeable future, there may continue to be a glycerol glut, which needs to be dealt with 5.20.2.3 5.20.2.3.1 Increasing the Value of Glycerol Purification of crude glycerol Glycerine produced from the conventional biodiesel manufacturing process is far from pure and can contain several impurities ranging from ash to metals (Table 1) The quality of glycerol in glycerine can be lowered when using less clean feedstocks such as food waste Removing such impurities is expensive, so the final product, whether pure glycerol or a derivative, must have high value for the purification process to be cost-effective Table Typical composition of the glycerol phase from biodiesel manufacturer [8] Content Amount Content Amount Glycerol content Ash content Moisture content 3-Monopropylenediol Methanol Organic, non-glycerol Sulfate Phosphate 77–90% 3.5–7% 0.1–13.5% Trace 0.01–3% 1.6–7.5% 0.01–1.04% 0.02–1.45% Na K Ca Mg Fe Mn Acetate 0.4–20 g kg−1 0.03–40 g kg−1 0.1–65 mg kg−1 0.02–55 mg kg−1 0.1–30 mg kg−1