FEATURE
DEVELOPMENT OF SOLAR MICROALGAE FEEDS
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by Dr Matthew Pearce, Director, Phycofeeds, United Kingdom
ew technologies take time to invent, time to prove to others of their technical feasibility, and yet more time to develop. As this article is being written, Phycofeeds is at an interesting stage of commercial development with its unique multi-disciplinary approach to a new feed technology, although it has yet to produce microalgae for fish feed trials. As such, this article comprises a “work in progress” for what could be a new technology of the future. To solve the feed production challenges of the future, we need to think and act innovatively, both in terms of financial business acumen and energy transformation pathways. Food, feed and energy will be ever more united in their provision. The author hopes to be able to write another article in the future to discuss progress on the fish feed trials. For now, let me tell you more about how I propose to get there.
Why solar?
For those who work in aquaculture regions within hot countries, you will know the power of the sun. For those of you who, like me, live in cooler climates, you will also appreciate the power of the sun when you travel abroad. The solar photovoltaic industry (PV) has grown rapidly in the past decade. PV generated electricity is one of the two forms of solar electricity, the other being from concentrated solar power (CSP). PV converts light directly into electricity. CSP focuses mirrors, transfers heat and light energy into molten salts, transports this energy, produces steam and via turbines produces electricity. Both have their advantages, PV can be used in cooler climates. Whilst CSP can only be produced in the sun-belt regions of the world, it can store energy at night. When peak demand for electricity occurs between about six and 10pm, electricity can still be provided from solar CSP even though the sun has gone down. As solar electricity production is commercially feasible, solar fuel production is not, yet. Phycofeeds aims to create a new energy transformation pathway from turning waste into biocrude using solar CSP. The HTL process has been done in the laboratory and is called hydrothermal liquefaction (HTL). Whilst both CSP and PV convert light or heat with time into electricity, HTL combines light or heat and pressure with time to convert carbon-based feedstocks into bio-crude. This process emulates what the ancient natural environment has already produced under the earth’s crust in the form of conventional crude oil, except Phycofeeds technology uses the sunshine of today, not yesterday to do it.
including site location, mirror aperture, geometry, solar tracking and environmental conditions. In particular, direct sunshine or dispersed sunlight from mist or environmental atmospheric pollution. Thermo-conversion of biomass or waste feedstocks into biocrude oil is a variation of a pyrolysis reaction whereby heat in the absence of oxygen increases the energy density of a fuel. For example, charcoal is a pyrolysis reaction derived from wood. Charcoal (30 MJ/kg) has an energy density greater than wood (20 MJ/kg). The temperature of the thermochemical reaction affects the product output. Using HTL, at low, mid and higher temperatures respectively, solids, liquid and gas fuel compounds are formed. The HTL reaction for the production of bio-crude oil is formed between 280-350°C and 150 to 200 bars of pressure. At this temperature and pressure, solid biomass or agricultural waste feedstock is converted into liquid bio-oil. However, although most of the carbon from the waste input goes into the resulting bio-oil, some carbon, nitrogen and phosphates relocate into the aqueous by-product output. That is where microalgae come in. Studies have shown that microalgae can grow using waste aqueous outputs from HTL because the waste contains carbon, nitrogen and phosphorus.
Phycofeeds approach
Industry creates a lot of waste, which isn’t always used as well as it could be. For example, sugar cane produces a by-product in the form of fibrous sugar cane bagasse, about four times more than the output of sugar. This is just one of four waste feedstock materials which Phycofeeds has tested, others being PET plastic, animal manure and microalgae. Waste material and water is placed within the focal point of a CSP demonstrator and heated to 320°C. The constant volume of the reactor vessel results in a pressure increase and converts solid
How does it work?
Solar CSP can achieve temperatures between 200-450°C. The variation between what can be achieved depends on many factors 14 | April 2018 - International Aquafeed