Sustainable Energy NZ #7 – Biofuel Bonanza? – NZ’s bio-energy potential

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!

Further Reading:

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.

10 thoughts on “Sustainable Energy NZ #7 – Biofuel Bonanza? – NZ’s bio-energy potential”

  1. “That said, algal entrepreneurs with a scalable design can send us their investor prospectus!”

    Proposition 1: Farm mangroves
    Proposition 2: Grow algae in tidal lagoons

    Mangroves While walking round the Manukau and subsequently canoeing old waterways to portages, with more to do, I became impressed with the exponential growth of mangroves in the Kaipara, the Manukau, and the Firth of Thames to name a few places where beaches and waterways are being lost to mangroves.

    Councils have an obligation to keep waterways open, but it is only use of waterways by boaties that keeps a handful going. I also learned the only people who approve of mangroves live on top of crumbly cliffs. Occasionaly people have got together and made illegal attacks on mangroves. Such actions have done little though I was pleasantly surprised when portaging from the Waikato to the Manukau last year to discover the mangroves had been removed from Port Waiuku and the channel reopened though not dredged. So I have been pondering how people might get to use the many waterways again, and wondering how much oil one could extract from a bucket of mangrove fruit. I have learned that mangroves have many commercial uses, including cooking oil, and the fruit is said to be edible.

    So there are large areas of untended mandrove farms in their anoxic beds of sulphurus mud, copiously supplied with nutrients by human activity, the mangrove habitats moving steadily south with warming. and expanded with the sediments of Auckland city expansion and intensive farming.

    Marine algae farming? Were the southwestern motorway passes Onehunga it cuts off a former bay, for hundreds of years the favoured beach for landing waka from the Waikato and Maukau. that area is now a park with a tidal lagoon. One hot summer that lagoon was taken over by large masses of algae rendering it an anoxic mess. They sealed out the tide and left the agae to rot, and stink, for months before restoring the lagoon Since then an improved management regime has kept the lagoon in a healthier state.

    Now you can see where I’m going. The requisit area can easily be found in the Firth of Thames. The necessary nutrients are already in oversupply. Perhaps only the output of the Piako and the western streams would be needed for nutrients and theWaihou guided along the holiday shore to keep the shore clean and provide a basis for public transport. Did I mention the demolition of bridges across the Waihou to save on holiday emissions? 🙂 🙂 🙂


    1. I just checked, Noel, and your mangroves are all – fairly unsurprisingly, given the latitude – Avicennia marina just like ours here in SA, so I’ll also point out the honey is really rather nice, too. Certainly the fragrance can be almost overwhelming sometimes.

      On the coast north of where I live there are several hamlets consisting of extensive rows of beachshacks looking out over dense mangrove forests – no, that wasn’t the original plan!

      Since ‘limited frost tolerances are thought to set th[eir] latitudinal limit‘ AGW should potentially provide opportunities for the southward spread of the species…

      1. I would like a taste of that honey.

        In 2004 a farmer’s wife living near Waiuku, on the southern arm of the Manukau first informed me of the frost sensitivity of mangroves and drew the link with global warming in their southward march. I found a Whites Aviation aerial photograph of Port Waiuku taken about 1940, no mangroves.

        I also saw a 19th century painting of a flour mill on a bit of east coast near Papatoetoe, South Auckland, no mangroves then, wall to wall mangroves now. However, I discovered in a bit of pre-european history evidence of mangroves in the Puhinui inlet , in the Manukau just near the Airport. not far from the site shown in the painting.



  2. The issue with algae-based fuels is simply one of thermodynamics and the practicality of dealing with huge volumes of water containing very small proportions of the product you need.

    The thermodynamics bit relates to the supply of the right proportions of the right nutrients at the right time and place. Expensive and difficult. To get the stuff you want you have to make sure all the other bugs n plants that like the same nutrient brew dont take over. Not easy to do in the lab. Very difficult in ponds of a size that is likely to be useful here.

    Then you have to run your brew of green or brown algae by pumps through concentrators to get something to dense enough to mess with in the fuel production unit. Again energetically expensive and capital expensive too.


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