8.1 THE BIOREFINERY CONCEPT

As a neologism, “biorefinery” was probably coined in the early 1990s by Charles A. Abbas of the Archers Daniel Midland Company, Decatur, Illinois, extrapolating the practices implicit in the fractionation of corn and soybean — the wet milling process was an excellent example of a protobiorefinery (figure 1.20). Certainly, by the late 1990s, the word (or, in an occasional variant usage “biomass refinery”) was becoming increasingly popular.1 The concept has carried different meanings according to the user, but the central proposition has been that of a comparison with the petrochemical refin­ery that produces not only gasoline and other conventional fuels but also petrochemical feedstock compounds for the chemical industry: from a biorefinery, on this formal anal­ogy, the fuels would include ethanol, biodiesel, biohydrogen, and/or syngas products, whereas the range of fine chemicals is potentially enormous, reflecting the spectrum of materials that bacterial metabolism can fashion from carbohydrates and other mono­mers present in plant polysaccharides, proteins, and other macromolecules (figure 8.1).

The capacity to process biomass material through to a mixture of products (includ­ing biofuels) for resale distinguishes a biorefinery from, for example, a “traditional” fermentation facility manufacturing acids, amino acids, enzymes, or antibiotics, indus­trial sites that may use plant-derived inputs (corn steep liquor, soybean oil, soy protein, etc.) or from either of the two modern polymer processes producing any one output from biomass resources that are often discussed in the context of biorefineries:

• Cargill Dow’s patented process for polylactic acid (“Natureworks PLA”), pioneered at a site in Blair, Nebraska; this was the first commodity plastic to incorporate the principles of reduced energy consumption, waste genera­tion, and emission of greenhouse gases and was awarded the 2002 Presi­dential Green Chemistry award.2

• 1,3-Propanediol (1,3-PD) produced from glucose by highly genetically engineered Escherichia coli carrying genes from baker’s yeast and Kleb­siella pneumoniae in a process developed by a DuPont/Tate & Lye joint venture; 1,3-PD is a building block for the polymethylene terphthalate poly­mers used in textile manufacture.3

However good are these example of the use of modern biotechnology to support the bulk chemistry industry, they center on single-product fermentations (for lactic acid and 1,3-PD, respectively) that are not significantly different from many earlier bacte­rial bioprocesses — in particular, lactic acid has a very long history as a microbial ingredient of yogurts and is used in the food industry to control pH, add flavor, and

control microbial growth in products as diverse as alcoholic beverages, frozen desserts, and processed meat; the lactic acid production sector has major manufacturers in China, the United States, and Europe that utilize lactobaccili, bacilli, or Rhizopus molds in large-scale fermentations.

The following three definitions for biorefineries focus on the multiproduct (usu­ally) biofuel-associated nature of the envisaged successors to fossil-based units:

1. The U. S. Department of Energy: “A biorefinery is an overall concept of a processing plant where biomass feedstocks are converted and extracted into a spectrum of valuable products.”4

2. The National Renewable Energy Laboratory: “A biorefinery is a facility that integrates biomass conversion processes and equipment to produce fuels, power, and chemicals from biomass. The biomass concept is analogous to today’s petroleum refineries, which produce multiple fuels and products from petroleum.”5

3. “Third generation (generation-III) and more advanced biorefineries … will use agricultural or forest biomass to produce multiple product streams, for example ethanol for fuels, chemicals, and plastics.”1

In early 2008, no such biorefineries exist, but the concept provides a fascinating insight into how biofuel-production facilities could develop as stepping stones toward the global production of chemical intermediates from biomass resources if lignocel — lulosic ethanol fails to meet commercial targets or if other developments (e. g., the successful emergence of a global hydrogen economy) render liquid biofuels such as bioethanol and biodiesel short-lived experiments in industrial innovation.[64]

The sheer scale of chemical endeavor possible from biomass resources is moreover extremely persuasive:6

• By 2040, a world population of 10 billion could be supported by 2 billion hectares of land for food production leaving 800 million hectares for nonfoods.

• With a “modest” increase in agricultural productivity to 40 tonnes/ hectare/year, this land surplus to food production could yield 32 billion tonnes/year.

• Adding in 12 billion tonnes annually from forests and other agricultural waste streams yields 50 billion tonnes.

Of this total, only 1 billion tonnes would be required to generate all the organics[65] required as chemical feedstocks — leaving the rest for biofuels, including traditional biomass as a direct source of power and heat.

Calculations prepared from and for German industry show that agricultural waste only, that is, cereal straw, could match the total demand for E10:gasoline blends as well as all the ethylene manufactured for the national chemical and plas­tics industries plus surplus ethanol for use in E85 blends and other chemical uses (figure 8.2).7

Included in the range of roles proposed for biorefineries, as codified by biorefin — ery. nl, the umbrella organization in the Netherlands tasked with developing strategic aspects of biorefineries (www. biorefinery. nl), are the following:

1. Primary processing units for waste streams from existing agricultural endeavors

2. Essential technologies for ensuring that biomass-derived ethanol and other biofuels can be produced at costs competitive with conventional fuels

3. New additions to be integrated with the infrastructure of agricultural processing — these might include (in Europe) beet sugar refineries

As corollaries and (probably) axiomatic truths, biorefineries will only become “interest­ing” (as players in the industrial economy) when they reach large scales of operation and contribute significant amounts of materials to widely used and/or specialist chemistry platforms while being driven not essentially or solely as means to reduce greenhouse gas emissions[66] but by considerations of the future depletion of fossil fuel reserves and the desire to broaden the substrate base, with governments being instrumental in cata­lyzing these developments by favorable taxation regimes and economic subsidies.