Welcome to the seventh post in the Sustainable Energy without the Hot Air – A New Zealand Perspective series. Today we’re crunching the numbers on the potential for biofuels in New Zealand. For the background to the work please our introductory post here. Also check out our earlier posts on the potential of hydro power, geothermal and wind, and the summary on the big three. Yesterday we dealt with solar (and found it was pretty big!). Note: the units are in kWh/day/person – that is, if you ran a 40W lightbulb for 24 hours, it’d take ~1 kWh over the space of a day. We then divide it by person to give you a sense of the scale of the resource proportionate to the size of the population. Be sure to check out the methodology. For reference – we’re looking to replace around 55 kWh/d/p of energy currently generated by fossil fuels.
Energy problems are just one of the significant challenges facing our civilisation so we are reluctant to consider options that affect food production or contribute further to soil degradation. However, as we transition away from liquid fuel-based transportation, biofuels could play a role in keeping us mobile.
We estimate that we need at least 9kWh/d/p of diesel for agricultural and heavy trucks. The best temperate crop-to-delivered-diesel is estimated by MacKay to provide 0.5W/m2. Therefore we would need 223,800 ha or 21% of all arable land to supply the required diesel.
There are extravagant claims being made for algal biofuel. Yields of 4.6 to 18.4L/m2 (5-21W/m2) have been suggested but the higher figures are really only obtainable in CO2-enriched water with complete control of temperature, light, and nutrients. Achieving these yields on an industrial scale will be a challenge. Since 2009, the sole commercial scale algal biofuel plant that has come online (based in New Mexico, USA) only produces around 100 barrels of oil a day, not even a drop in the ocean of the 150,000 we consume daily in New Zealand. Furthermore, where is the CO2 to come from? Using CO2 from thermal power stations to generate biofuel is not CO2 sequestration – the CO2 still ends up in the air when the diesel is used. So what if only CO2 emissions from steel production are used? Glenbrook uses 800,000 tonnes of coal pa, so provided you can find 20,000ha of suitable agricultural land nearby, then this will supply 6kWh/d/p of algal diesel for around ⅛ of the equivalent area for fuel crops.
Finally, let’s consider New Zealand’s total biofuel potential. MacKay includes the solar component present in food when adding up energy costs, and also makes a calculation for biofuel production potential for the whole of UK. What potential biofuel production could be obtained in NZ? According to MAF [cewg8p], NZ has 14.7 million ha in production for either food or plantation forest (of a total NZ land area of 27 million ha). Converting that to biofuel at a rate of 0.5W/m2, gives a massive 373 kWh/d/p. Admittedly getting 0.5W/m2 off hill country land might be difficult but even using just our arable land (~1.5million ha) would still yield 43kWh/d/p (enough to power our car fleet as we shall see).
NIWA has worked on this issue as part of its BioEnergy Options for NZ pathways project [dyqotee], and determined that ‘energy forestry’ could produce all our liquid fuel and heating needs, but that it would take 3.2 million ha. Obviously, this a lot of land. Their analysis shows that much of the afforestation could be undertaken on marginal hill country that would minimise the impact on food production (and provide other positive benefits), but that it would only be economic at a large scale if the price of oil goes above $200. That said, all forestry residues from current production would sustain 10% of our energy requirements, meaning that it could be a piece of the energy supply puzzle. It’s worth remembering that NZ is not just a net exporter of energy, we are a net exporter of renewable energy via our food. We would argue that there are better uses for our land than growing fuel for transport.
Conclusion: Biofuels are feasible at the expense of considerable agricultural intensification, or on marginal land if the price of oil goes up. The important thing to note is that their energy conversion (turning m2 of sunlight into usable energy) are several factors lower for biofuels (0.5W/m2) than solar (PV @ 5W/m2 or thermal @ 15W/m2) – thus, we need a lot more land to generate the same amount of energy – though obviously they’re in different forms. That said, algal entrepreneurs with a scalable design can send us their investor prospectus!
We should give a heads-up to NIWA for their EnergyScape work on Energy Forestry. They’ve done some pretty intensive analysis on what sort of potential NZ has for forestry.
Do the Math’s Tom Murphy has an excellent analysis of the challenges of scaling biofuels, and the implications on infrastructure.
An article on the state of the biofuel industry in New Zealand by Chris Barton of the New Zealand Herald. He outlines the need for bio-refineries that we haven’t outlined in this paper as we’ve concentrated on the scale of the resource. It would appear that we’d need to build substantial infrastructure to develop these biofuels into usable products.