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Microalgae for energy production and nutrient recycling

Microalgae for energy production and nutrient recycling. Nicola Wood, Student Sustainability Conference, 29 th March 2019. Source: UN Sustainable development Goals. Energy. Fossil fuels are estimated to account for 78% of global energy consumption as late as 2040 (IEO, 2016).

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Microalgae for energy production and nutrient recycling

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  1. Microalgaefor energy production and nutrient recycling Nicola Wood, Student Sustainability Conference, 29th March 2019

  2. Source: UN Sustainable development Goals

  3. Energy • Fossil fuels are estimated to account for 78% of global energy consumption as late as 2040 (IEO, 2016). • Global energy demand is set to rise by 50% between 2012 – 2040 • Oil, gas and coal are predicted to run out as early as 2066, 2068 and 2126 respectively • Atmospheric greenhouse gas levels are at a record high • Increasing occurrence of weather extremes are believed to be connected with increasing atmospheric CO2 • Global sea level rises by approximately 2.0mm per year Sources: https://oceantoday.noaa.gov/happennowarcticseaice/; National Oceanic and Atmospheric Administration

  4. FOOD • Sustainable food production requires arable land and large quantities of clean water and fertiliser. • The Haber-Bosch process to create ammonia from atmospheric nitrogen and hydrogen requires 1-2% of all global energy and requires approximately 2L fossil fuel to produce 1kg of nitrogen for fertiliser. P • World consumption of P2O5 is set to rise by 10% in the next 4 years. • Phosphate is not an infinite source!

  5. World Phosphate Reserves Sources: US Geological Survey, 2014; http://www.potashcorp.com/overview/nutrients/phosphate/overview/world-phosphate-rock-reserves; Source: http://www.indexmundi.com/commodities/?commodity=rock-phosphate&months=180

  6. Water • An average city of 500,000 inhabitants produces approximately 85,000 tonnes of municipal wastewater each day all of which needs to be treated. • Leeds produces approximately 130,000 tonnes per day • Despite our reliance on nutrients for fertiliser, most of the nutrients we currently use end up lost through wastewater treatment processes

  7. Bioenergy-the solution to our energy problems? • If 10% of the sun’s energy reaching earth could be harnessed, total human energy demand could be satisfied by an area equivalent to 0.07% of the earth’s land surface • But biomass production for energy is severely limited by the availability of land and fresh water. CO2 CO2 The ‘Food vs. Fuel Debate’

  8. Microalgae • Diverse group of eukaryotic single cell organisms. • Can grow efficiently on non-arable land – do not compete with food for land • Do not require a fresh water supply • Increased efficiency of energy to biomass due to their simple structure • Much greater oil yields than most plants • Neutral lipids, triacyglcerols (more commonly referred to as oils) are the starting product for biodiesels. • TAGs can be turned into biodiesel via a transesterification process and used similarly to regular diesel fuel.

  9. BUT… • Current fuel prices at pump are approximately $0.60-2.30 across the world • In order to be economically viable, microalgal biodiesel must therefore be comparable in cost. • The cost of microalgal biodiesel need to fall by approximately 5-7 times current costs So… • Combine microalgae with wastewater treatment • Microalgae have naturally high N (~10%) and P (~1%) contents meaning they offer the ability to remove high quantities of nutrients from waste streams Source: Delrue et al 2012

  10. The Closed Loop Cycle

  11. So, Where are we up to? • Microalgae grow well in a variety of wastewaters to high biomass yields • Microalgae can successfully remove almost all N from wastewater streams. • But, the only known triggers of oil accumulation are from high stress leading to cessation of growth and limited biomass yields • The conditions needed to optimise phosphorous accumulation are poorly understood

  12. A Compromise Biomass Phosphorous Oil • Optimised by high carbon, nitrogen and phosphorus supply • Optimised by nitrogen starvation and high carbon availability • Optimised by high phosphorus concentration with/without pre-starvation period

  13. What Next? • Genetic modifications • Looking at lesser studied triggers for oil accumulation • pH • Sodium bicarbonate addition • Phosphorous starvation • The effect of different nitrogen sources

  14. Thank you for your attention Any Questions?

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