Biomaterials

Biological Production of Fuels and Chemicals

Rafael Luque, Chun-Ping Xu, Rafael Luque, Chun-Ping Xu

• Publisher: De Gruyter
• Year: 2016
• eBook ISBN: 9783110383584
• Edition: 1
• Topic: Technology & Engineering
• Subtopic: Biochemistry
• Index: Technology & Engineering

In times of declining fossil stocks, science and industry have to find alternative resources for the production of fuels and chemicals. This book presents techniques for the utilization of biomass and waste as raw materials for the production of platform molecules, biopolymers, bioplastics, and bioethanol. Latest research results as well as industrial application thereof are discussed.

Gareth M. Forde, Thomas J. Rainey, Robert Speight, Warren Batchelor, and Leonard K. Pattenden

1Matching the biomass to the bioproduct

Summary of up- and downstream bioprocesses

1.1Introduction

As noted by the science journalist Robin Williams, “The 20th century was the century of physics, the 21st century will be the century of biology”. Knowledge of biological systems started firstly with observation or documentation, followed by understanding, then finally utilization or biomimicking. Whilst humans have been employing bioprocesses since as early as 7000 BC (as evidenced by Neolithic fermentation jars), our detailed understanding of biological processes in terms of genomics, metabolomics, and proteomics is very recent.

For a production process to be economically viable, the availability of the feedstock, the unit operations and the product must be understood. Lower value products (e.g. livestock feed), bulk commodities (e.g. sugar) or products with a number of competing sources (e.g. electricity) require scale, low cost feedstocks (e.g. sourced from broad-acre, agri-waste or animal tissues), and either low cost or efficient unit operations (e.g. high yields, low utility requirements). Higher value biomolecules (e.g. enzymes; biopharmaceuticals) can bear higher cost feedstocks (e.g. from fermentation) with higher cost intensity unit operations (e.g. centrifugation, spray drying and chromatography). Fig. 1.1 shows some examples of biomass feedstocks or products and their associated value as a function of cellulose and hemicellulose content. Their abundance in many forms of biomass and their attractiveness for fuel drive down their price, but there is substantial opportunity for further value adding.

Biomass is inherent and, in the vast majority of cases, nontoxic as biological processes create products which serve as feedstocks for other processes (with notable exceptions, such as venoms and pathogens, representing extremely low percentages of the total global biomass). Hence, a well-engineered bioprocess should be “benign by design”. Bioprocess engineering is defined as the design and development of processes for the manufacture of products from biomass or via biological processes.

By using the inspiration offered by biological systems, bioprocess engineering should strive for creating circular processes where everything other than the end product can be a feedstock for another process. The inspiration to address many of society’s current challenges using biology has spawned the area of biomimetics, where an engineered biological system aims to mimic the inherent advantages of natural biological systems. An example is where humans look to biology for examples of biofixation of carbon dioxide (CO2). CO2 is taken from a gaseous phase and converted into biomass and biological compounds (e.g. carbohydrates, lipids, DNA, protein), then this biomass is reused as feedstock for products such as transport fuel, energy, polymers, food, food additives and fine chemicals. Whilst such systems may have inherent inefficiencies, if the net environmental impact is zero, then the economics may be improved through scale and smart engineering. Industry must find ways to achieve deep decarbonization of how energy, food and products (polymers, drugs, etc.) are created, that is, to stop the reliance on fossil fuels. Biomass processing coupled to innovative downstream processing provides one significant opportunity to decarbonize human society.

Fig. 1.1: Correlation of dry weight cellulose and hemicellulose content to value in $ per ton. Note that the x-axis is logarithmic.

Use of life cycle analyses (LCAs) can provide insights for making long term decisions on sustainable processes. For example, the biopharmaceutical industry has one of the highest waste to product ratios of any industry (kg waste generated per kg product produced) compared to the oil and gas industry which has the lowest waste to product ratio. This high waste ratio is caused by the extensive use of disposables and cleaning requirements warranted in the manufacture of a biopharmaceutical. One option to improve the sustainability of bioindustries (refer Fig. 1.2) is anaerobic digestion to produce bioenergy from organic byproducts, rather than chemical treatment or off-site disposal. Other examples include the recycling of nutrients or isolation of fractions from waste streams for other purposes such as carbon-fiber production from waste lignin.

This chapter will consider which biomass feedstocks are most suited for the manufacture of bioproducts (e.g. bioenergy, chemicals, vaccines) via appropriate bioprocess engineering unit operations. For example, a low value biomass (chipped wood) requires simple, low cost and large scale unit operations whilst the manufacture of a high value bioproduct (e.g. a biopharmaceutical or functional food) utilizes a larger number of smaller scale and high cost unit operations to achieve appropriate purities. The chapter will consider upstream processes (the creation of the biomass), down-stream processes (the separation of the target biomolecules or value adding stages (refer Fig. 1.2 for a sample flow diagram) and finally present some examples of the creation of products from biomass.

Fig. 1.2: Block diagram of a bioprocess for the manufacture of a purified biomolecule via fermentation. The stage of product concentration and purification represents approximately 50 to 80% of total processing costs.

1.2Upstream bioprocesses

Upstream biomass generation can be in “open” or “closed” systems, where open systems are traditionally utilized for the generation of food and energy crops using agricultural or cropping processes, whilst closed systems are routinely characterized by monocultures (e.g. bacterial, yeast) achieved via the use of sterile procedures with defined or semi-defined media.

1.2.1Open systems

Food, forestry and energy crops are typically based around sugars, starch and lignocellulosic material. Harvesting operations for many food industries involve leaving some nonfood material in the field (e.g. stubble from grain or leaves from sugarcane) while the harvested material is separated into (i) food and (ii) nonfood material. The greater the chemical complexity of the nonfood material (e.g. lignocellulosics), the more challenging is the processing and value adding. Similarly timber is harvested, sawn to produce lumber and the residue is chemically complex which results in much of it being burned (Section 1.4.1). Notwithstanding, open systems can produce high value materials – an example is provided in Section 1.4.5.

Typical sources of biomass from open systems:

–Food agriculture

–Sugarcaneindustry

–Grain industry

–Fruit and vegetable

–Otheragriculture

–Cotton

–Dedicated energy crops (e.g.miscanthus)

–Forestry

–Timber

–Bark

–Woodchip

–Leaves, branches, stumps

The products from biomass are wide (in order of increasing value):

–Electricity

–Buildingproducts

–Transport fuels

–Food

–Pulp and paper products

–Newsprint

–Photocopier paper

–Tissue

–Niche materials (e.g.microfibrillated cellulose)

Typical upstream operations include:

–Planting

–Crop maintenance (e.g. fertilizing, spraying, pest control)

–Harvesting

–Transportation

–Coarse separation of the plant into different components (e.g. grain from husk and bark from the timber) by mechanical processing

–Combusting part of the feedstock may occur to assist upstream processing (e.g. sugarcane)

1.2.2Closed systems

For closed systems biomass is composed of cells which may, from an engineering perspective, be considered as a highly organized molecular factory, see Fig. 1.3. Our modern understanding of cells is not perfect clones of the same cell, but rather colonies of interacting cells with specialized functions.

Fig. 1.3: Upstream or BIOREACTION section: Selection and conversion.

Deloitte Touche Tohmatsu [1] reports that global fermentation industries are valued at over US $ 127 billion per annum made up of ethanol (87% of value) with the next two largest groups being amino acids (8.7%) and organic acids (2.8%). The projected annual growth to 2020 (excluding alcohols) for fermentation products is 6.5%, in which the highest growth area is polymers.

The primary characteristics of a cell are the cell membrane (or plasma membrane), cytoplasm and organelles and the nuclear reg...

Table of contents

• Cover
• Title Page
• Copyright
• Contents
• List of contributing authors
• 1 Matching the biomass to the bioproduct
• 2 Systems biology in biofuel
• 3 Production and application of chitin
• 4 Biological production of welan gum
• 5 Utilization of food waste for fermentative hydrogen production
• 6 Bacterial dye-decolorizing peroxidases
• 7 Biological routes to itaconic and succinic acids
• 8 Novel nanoparticle materials for drug/food delivery-polysaccharides
• Index
• Endnotes