Unfactory Alternatives
Next: Overview of polymers
Before dwelving into what types of goods the unfactory enables to produce locally, its good to note that it is not by any means the only option to decentralise creation of chemical and medical feedstocks and enable production of a multitude of things.
Lets take a brief detour to the other unfactories that are possible.
Biorefinery
A biorefinery is a refinery that converts biomass to energy, chemicals or food additives. The core idea is to use the hard parts of plants and other currently unused residues and make them into more valuable products.
Biomass includes agriculture crop residues such plant straw, leaves, forest residues, special crops grown specifically for energy use like switchgrass, organic municipal solid waste and animal wastes. These can broadly be categorised to virgin biomass (natural trees, grass), waste biomass like existing industrial byproducts (corn stover, cooking oil) and energy crops (e.g, willow specifically grown for it). It’s also possible to use food source such as corn as a feedstock but the trend is to move away to use currently unused sources.
Biorefineries can produce a wide variety of end products such as food, feed, fuel and chemical materials. The same biorefinery can be made to produce both one or several low-volume but high-value chemical or nutraceutical products and a low-value, but high-volume liquid transportation fuel such as bioethanol or biobutanol.
There are two main ways a biorefinery can work. Either by breaking the sugars of the plants into more useful end results like ethanol using fermentation and other biological means or by thermochemical process by using high heat and chemicals to break the organic material to more simpler molecules. Both ways can produce fuels and chemicals like methanol, ethanol and polymers.
There is a wide variety of options based on available raw materials and what the markets need. We’ll just briefly mention some main concepts.
Sugar Way
The sugar way is based on first breaking biomass into sugars that are soluble in water. This breaking is done either with chemicals or microbes. These sugars can then be transformed to ethanol, aromatic hydrocarbons and liquid alkanes with fermentation, dehydration or aqueous-phase processing.
The residues – mainly lignin – can be used for power generation for the biorefinery or may be upgraded to produce other products.
The difficulty in using the polysaccharides in plants (long chains typically made of simple sugars) comes from lignocellulose. Lignocellulose is an extremely stable three-dimensional network of lignin and cellulose. Cellulose is a linear polymer of several hundred to thousands of glucose unit and lignin is a complex cross-linked polymer of phenols. Lignocelluloses give plants their rigidity and protect them from herbivores and pathogens.
The great stability of lignocelluloses means that to make the carbohydrate available for fermentation requires costly mechanical and chemical pre-treatment. Cellulose requires further processing to produce fermentable sugars either with acid treatment or cellulaze enzymes. Once these sugars are produced, the fermentation happens similar to fermenting starch-based materials (beer et al.).
To develop good processes for bioconversion to ethanol, an organism is needed that uses all sugars ( C-5 and C-6 sugars) produced in earlier phases in an environment where concentration of alcohol is high and it needs to happen at high rate. Finding such organisms is one of the difficulties in developing biorefinery technology.
In addition to being a fuel, ethanol is used as the feedstock for a wide range of chemicals, including acetaldehyde and acetic acid that in turn are used in manufacture of fibers, plastics and explosives, perfumes, dyes and drugs.
Methane (synthetic natural gas) can be made from non-woody biomass by anaerobic digestation by micro-organism in an environment with no oxygen. The output is methane, carbon dioxide and a nutrient rich residue that can be used for improving the soil.
Biomass Gasification
Gasification is a process that converts biomass into carbon monoxide, hydrogen and carbon dioxide. This is done by heating the material at high temperatures >700 °C with low level of oxygen so that it does not burn. Controlled amount of steam or oxygen are added during the process. What comes out is syngas. Gasification is a flexible process meaning that any biomass including waste can be used. Syngas itself is a fuel or can then converted into useable fuels and chemicals, for example, hydrogen, methanol and ethanol.
Syngas can also be converted to a mixture of alkanes by the Fischer-Tropsch process as already discussed.
Biomass Pyrolysis
In pyrolysis biomaterial is heated to a high temperature without air to produce bio-oil. The reaction time must be very short or material will turn to carbon (char). The generated bio-oil is an easily stored and transported liquid that can directly be burned for heat but can also be turned to liquid fuels for gasoline or diesel engines or as a source for chemical production.
Microbes
Third alternative for the Unfactory is via genetic modification. In posts on Health we discussed biosimilar drugs that are made with living cells by injecting genes that produce the needed protein. Same mechanism can be used to have microbes produce also food like egg white and many chemicals. Microbes could also be enhanced to make different kinds of fuels. For example, certain cyanobacteria produce naturally pentadecane that is a common hydrocarbon in diesel fuel. Fore more.
I’ll leave working out the kinks of this path to the gentle reader.
Biomimicry
Fourth approach for decentralizing production is quite different and comes from the field of biomimicry. Biomimicry is a movement where nature is used as an inspiration and blueprint for the production of materials or creation of systems.
The system wide approach looks to form production processes that form closed loops. In a closed loop the waste product of one phase is the valuable input to the next one.
Let’s take an example from beer production. Brewing creates a side stream of spent grains that still contain valuable proteins and other nutrients. Sometimes used as animal feed but not very good as they are tough to ingest.
Zeri.org has created a system where used grains are used for growing mushrooms. The mushrooms also make the grains more digestible for animals and as added benefit increase protein content, making it an improved feedstock.
The livestock produces waste that can be fed into a digester with waste water also coming from brewing (making a liter of beer consumes about 20 liters of water, thus creating a big stream of waste water). Digester in turn produces methane to be used as fuel or feedstock for chemical processes. In addition, the digester creates a nutrient solution that can be fed to algae. The algae digest the nutrients in the solution through photosynthesis. The algae in turn can be fed to fish.
These kind of interdependent production flows resemble natural ecosystems. Biomimicry approach would systemically try to identify as much as possible such processes and test them in any given environment to see how well they would work.
So this is in essence a production technology built on waste and sidestreams of other production processes and trying to extend them as long as possible and to finally close the loop.
Comparison of Unfactory Concepts
The two first unfactory models (based on captured carbon from air and biorefinery) of this chapter have similar characteristics. They both lend themselves well to decentralization.
Biomass is a continuously replenishing raw material that is everywhere, its hard parts are poorly used today and can replace oil. Every nation can be a bio-oil producing country meaning that it cannot be used as a control point in competition between nations.
Same is true when decentralised electricity is used to power up the process of making synthetic hydrocarbons. The scale of decentralisation differs from small in solar to medium in SMR and geothermal.
The third option lends itself to decentralisation once the right genetic modification has been made. As creation of the production micro-organisms requires advanced skills, the initial step most likely needs to be done centrally.
Biomimicry based approach again is something well suited for decentralisation requiring no new technologies to be used unlike any of the above models. It’s mostly useful in food production and finding uses for side streams of industries to lesser extent.
Next: Overview of polymers