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My exploration of alternative "green" fuel options

A quick Google search explains that sustainability is the ability to be maintained at a certain rate or level. A recent update states that sustainability is avoiding the depletion of natural resources to maintain an ecological balance. Put both of those together and I hope we have a future where we don't just maintain our natural environment, but we avoid an ecological disaster.


I recently undertook some studies with the University of Canterbury to better understand how businesses can achieve net zero carbon emissions in order to do our part in controlling global warming. The premise of that course required the participants to understand that we can not continue to use fossil fuels in the manner we have been. We as a society must downshift our reliance on finite resources.


One of the modules explored current alternative fuel sources and I learnt some astonishing information. Energy return on investment (EROI) is a formula that compares the energy used in the production of an energy source, compared to the amount of energy that source makes available. Factors such as production costs, storage of energy, and conversion of that energy are all factors that reduce the amount of useful energy available for consumption compared to the amount of energy required to produce that energy.


A low EROI means a lot of resources are being used, and greenhouse gasses are being pumped into the atmosphere, yet there is little to no return on that investment. Additionally, energy profitability calculates the net energy divided by energy production Many energy sources are currently sort after as alternative sustainable energy to replace fossil fuels, for example, Hydrogen. According to the US Department of Energy, Hydrogen has the potential for near-zero greenhouse gas emissions which they state holds promise for growth in stationary and transportation energy sectors. However, Hydrogen as a fuel source has a negative EROI, which means it takes more energy to create hydrogen as a fuel source than it makes available for use. Yet the State of California is offering rebate incentives for consumers to purchase Hydrogen fuel cell cars as part of a clean vehicle initiative.


Another renewable energy source is hydroelectric dams, which NZ has as an energy source. The electricity generated could be used an alternative fuel option to fossil fuels for vehicles. The New Zealand (NZ) Government is offering a clean car rebate for electric vehicles, which seems attractive as Hydro dams have a high EROI of between 40-50 and a high energy profitability of 80% return on investment.


While NZ does have Hydroelectric dams, NZ also has geothermal, biogas, wind, diesel, coal/gas and gas power stations all contributing to the electricity used to charge the electric vehicles. And the embodied carbon that is generated due to the extraction of lithium, cobalt and other metals used in the manufacturing of electric vehicle batteries should not be ignored.


Geothermal energy stations generate a subsistence EROI of between 6-18, which means the return on energy is borderline into decline with energy profitability of 67%. Wind farms perform slightly better than geothermal energy with a large range of EROI of between 7-27 and an energy profitability of 70%. The wide range of wind farm EROI means that sometimes the wind farm energy generation could be in the subsistence range, but can also be in the declining return bracket.


According to the Electricity Authority of NZ, more New Zealanders are choosing to put solar panels on their homes to generate electricity. However, from an EROI perspective, solar energy provides an EROI of between 3-10 with a net profitability of about 55% which is lower than wind and geothermal energy sources. But solar energy does put the capability of generating a personal electricity supply, directly into the consumer's hands.


The University of Michigan considers that wood-based thermal energy is the key to producing sustainable and renewable heat and suggests that wood pellets and cordwood are better for heating small spaces like homes. However, thermal wood generates an EROI of 10-25, which is better performing than solar and geothermal, but thermal wood has a net energy production of only 47% which is lower than nearly all other forms of "green" energy.


The last and least capable "green" energy source is Bio-Ethanol. According to the Bio-Energy Association of New Zealand, Bio Fuel is a 21st-century, green, sustainable bioenergy offering the most flexible and extensive renewable source of energy. Bio-Ethanol comes from whey, a dairy by-product which is mixed with petrol to make a bioethanol blend which most new vehicles can run on. However, biofuel feedstocks require changes to land use, can put pressure on water resources, can generate air and water pollution and can increase food costs. Additionally from an EROI perspective, Bio-Ethanol generates the lowest EROI after Hydrogen at 0-6 with a net energy of 4%.


Overall, there are many types of renewable energy sources, with the highest-performing being Hydroelectric dams, and the lowest-performing being Hydrogen and Bio-Ethanol. With these alternative "green" fuel sources not actually performing as expected, it is the downshift in our use of fossil fuels, not just a switch to green alternative energy that will aid in our end goal of avoiding ecological disaster.



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