Emissions GR Policy Renewables Scenarios

Log, slash, truck and burn – welcome to renewable electricity nirvana

Guest Post by Geoff RussellGeoff is a mathematician and computer programmer and is a member of Animal Liberation SA. He has published a book on diet and science, CSIRO Perfidy.

Back in 2011, the federal Department of Climate Change and Energy Efficiency commissioned the Australian Energy Market Operator (AEMO) to investigate two future scenarios in which the National Electricity Market was fuelled entirely by renewables … as defined by the Department. An essential component of AEMO’s 100 percent renewable solution involves the annual transport of 50 million tonnes of plant material from farms, native forests and plantations in what can only be described as a massive soil mineral mining operation. Log, slash, truck and burn. For details read on.

AEMO has just released draft findings and been met with typically enthusiastic headlines among renewable advocates: “100 percent renewable is feasible: AEMO” and “100% renewables for Australia – not so costly after all”. It took the Financial Review to point out that “not so costly” means doubling the wholesale price of electricity. The AEMO report was welcomed by the Australian Conservation Foundation “100 per cent clean energy on the way”.

Martin Nicholson on responded quickly saying it’s possible to meet the modelled electricity demand using nuclear power for less than half the lowest cost scenario of the AEMO report. This is $91 billion compared to the range estimate of $219 to $332 billion for 100 percent renewables with Nicholson using the same source of costing estimates as AEMO.

A nuclear solution would also avoid some of the uncosted gotchas, the extra “challenges” contained in the report: land acquisition of half a million hectares, boosting the distribution network, electric vehicle charging infrastructure, biomass logistics infrastructure, and DSP. What’s DSP? … demand side participation. A wonderful piece of euphemistic jargon whereby people either do without or get their electricity at some inconvenient time. E.g., Why cook dinner when you get home from work when you can cook it at lunch time when the solar PV is powering and just re-heat it later? All you need is the will and a new oven remotely controlled by your smart phone. I call it the demand side kitchen rules.

Let’s first sketch AEMO’s broad findings before looking at the most contentious issue.

Climate change isn’t just about electricity

Firstly, note that the study doesn’t deal with Western Australia or the Northern Territory. It’s strictly about areas in the NEM (National Electricity Market), the eastern Australian grid.

Second, the AEMO study is about electricity. Electricity is about 1/4 of our fossil fuel energy use, and about 230 of our 580 million tonnes of CO2eq (carbon dioxide equivalent) greenhouse gas emissions. The AEMO study dealt with switching to electric vehicles by assuming that all charging would be done at times of high solar PV output and would thus absorb it’s entire assumed rooftop PV output.

So the AEMO study isn’t a total climate change action plan. It’s just one component.

Base-load power and lunch bars

But the AEMO study authors understand electricity systems. They understand the value of systems you can control compared with systems you can’t. In traditional power systems, demand is uncontrolled while the supply is adjusted to match. Typically decisions are taken every 5 minutes about which power sources to crank up or throttle back.

But high profile renewables, like wind and solar power, reduce the elements of the system that a manager can control while simultaneous increasing the parts they can’t. The traditional system works like an inner city lunch bar. The boss has a couple of permanent staff and tries to hire just enough casuals to cope with reasonably predictable peak periods. The permanent staff are like the base-load part of a normal system.

Building a 100 percent renewable system is like operating with no permanent staff and where the casuals rock up (and leave) when they feel like it.

AEMO’s solution isn’t to abandon the base-load concept but to build a partial base-load system from biomass or geothermal power, supplement it with concentrating solar thermal (mirrors heating water making steam driving turbines) with molten salt storage and to roster double the number of casuals like wind and solar in the hope that they’ll be around when needed based on past behaviour. After all, how different could future weather patterns be from the past?

Wind and solar contributions to the power system in the immediate future are somewhat predictable if you throw enough research dollars around. You can, for example, monitor cloud cover with satellites and use super computers and weather modelling to predict wind speeds 24 hours in advance … but however good your predictive capacity may be, wind and solar can’t be powered up to deal with surprising demand increases. Providing too much power is also a problem and one that costs money to solve. For example, the Czechs are having to add grid infrastructure to allow them to lock out excess German renewable electricity flowing across interconnectors.

AEMO’s base-load renewables

So how does AEMO’s electricity lunch bar fly?

I’ll only consider the second of two scenarios considered by AEMO. The first scenario only supplies 300 TWh/yr by 2050. This is inconsistent with any serious concern for climate change which will require far more clean electricity than this to replace as much as possible of our full gamut of fossil fuel use. The first scenario also relies heavily on geothermal power which has so far promised much and delivered nothing.

The second scenario aims for about 370 TWh/yr by 2050. This is rather closer to what is required. In addition, the second scenario relies heavily on biomass with less geothermal. Regardless of the geothermal outcomes, the biomass component of scenario two requires considerable comment.

AEMO uses three grand assumptions to make scenario two feasible:

  • First, it presumed a base-load supply driven by biomass and geothermal power.
  • Second, it presumed it could shift peak demand from when the sun wasn’t shining much in the late afternoon to somewhat earlier when it was.
  • Lastly, AEMO postulated heavy use of concentrating solar thermal power with molten salt storage.

These are AEMO’s key responses to what it calls the challenges of a 100 percent renewable system. The word challenges gets plenty of use in the report!

Let’s consider these assumptions:

What’s biomass?

Biomass in this context is plant material. Mostly we eat plants, and they provide about 83 percent of global calories, but burning plant material, mainly wood, has always been popular and deadly.

Wood smoke from cooking fires causes about 3.5 million premature deaths a year, including 1/2 a million children. It’s been poisoning the air, killing children and damaging our cellular DNA throughout our evolutionary history. And it’s not only the smoke that is a problem, wood dust is a demonstrated human carcinogen, so any increase in people working at the wood face will present OH&S health challenges. A 2012 Italian study called for research on the health impacts of emissions from power plants fueled by solid biomass … there’s been little work. A recent Spanish study found that “wood-processing-plant” operators had a particular and significant stomach cancer sub-type rate 8 times higher than normal. There hasn’t been enough work to take this figure as face value, but it should certainly be taken very seriously because it’s a rate increase of a size normally unseen outside of tobacco studies. Most focus on wood dust has been on lung cancer because of the obvious pathway with fine particles lodging in lungs, but what ends up on their sandwiches may be a bigger problem for workers in wood dusty environments.

Biomass may be natural, but working with it isn’t always benign. Nor is there anything necessarily renewable in any relevant sense about biomass production systems. More on this later.

AEMO envisages biomass coming from various places: 1) stuff left over after a harvest, typically called stubble or crop residues, 2) suburban waste, and 3) native and plantation forestry “waste”. AEMO contracted CSIRO to provide biomass expertise and the resulting CSIRO report makes for interesting reading. They envisage planting 4.8 million hectares of good farmland with fast growing trees to provide 20 million tonnes of timber to pulp and burn each year with correspondingly reduced food output. The idea takes some beating in the selfish and unethical stakes. Thankfully, AEMO didn’t go for this option.

What they did go for was a biomass base-load system which, by 2050, would require shifting 50 million tonnes of plant material annually to a huge network of furnaces connected to turbines connected to some kind of grid attaching to the NEM. This 50 million tonnes is slightly more than we typically shift during our annual grain harvest as food.

Is biomass a renewable resource?

Any reasonable backyard gardener knows that, with a couple of exceptions, everything you take out of a garden has to be put back. It doesn’t get back by magic. It’s not like solar power. A crop of lemons removes (among other things) iron, so you sprinkle iron chelates around the tree. Similarly, the backyard gardener with a few chooks may praise the chook manure, but the real input is the chook pellets from the grain store. These are liberally laced with minerals but also embodying the minerals added to croplands by the farmers who grew the grain. The chooks merely spread it around and add a rapid composting component to enhance the availability of the nutrients.

When you remove crop residues after a harvest, you are mining the minerals embodied in the plant matter and removing them from the soil. But the negative impacts don’t stop there. Here’s a chart from one of the world’s foremost soil scientists (Rattan Lal) outlining the chains of adverse impacts.

Spend some time reading the above image. I won’t waste space expanding on all the points, but will note that it’s not only the minerals which disappear and need to be replaced, removing stubble may also cause the carbon content of soil to decrease depending on a complex mix of factors. This isn’t rocket science, it’s much harder with many more constantly changing variables. Soil nutrient depletion may turn out to be the least of the problems.

According to Lal, cropping can be done in ways that increase soil carbon, but that’s not (overall) how we do it in Australia. Our croplands have been losing about 17 million tonnes of carbon per year over the past twenty years. And probably much more for decades before that, but it’s only in the past 20 years that we have been measuring the losses and reporting on them (to the UNFCCC).

So if we can’t even crop without losing carbon, what are the chances we can remove even more plant material during the process and do it properly? Zero would be a pretty safe bet.

Some years back when Jared Diamond wrote in “Collapse” about Australia’s farmers mining the soil, he received plenty of flack. But our carbon inventory data demonstrates the accuracy of his claims. Certainly, there are many farmers operating benignly, but it’s our net average which matters and that net average sucks.

With Australia’s track record, calling electricity from biomass “renewable” is, at best, a pipe dream.

Another of the big biomass streams in the AEMO base-load system is urban waste. For a renewable energy system to be predicated on high levels of suburban waste, including food waste, is rather bizarre. What happens if people finally start listening to the constant barrage of messages to stop wasting food? To start using composting systems? To dig up the fence to fence concrete and plant veggies? A shrinking waste stream might be unlikely, but it would certainly knock a hole in AEMO’s biomass budget.

Lastly, AEMO wants to get more biomass out of both our native and plantation foresting operations. Why pull any material from a native forest without a pressing need? It may be waste to us, but to an bird it’s nesting material or the nest itself. Many of the crop residue problems apply similarly to tree harvesting operations, whether in native forests or plantations.

The CSIRO report on which AEMO based its modelling is explicit in stating that it didn’t consider the constraints of logistics or economics, but strictly what quantities of biomass could be produced. The report didn’t even bother saying that it didn’t consider the impacts on wildlife of or food production of such operations.

The following image indicates that by 2050, if you can hit the 50 million tonne biomass mark, you can get 57 TWh/yr from it (in scenario two).

In easily remembered round numbers, it takes a million tonnes of stubble pulled off about a million hectares of crop land and transported in 40,000 x 25 tonne truck loads to produce 1.1 terawatt hour of electricity. The adverse consequences could spread far and wide with topsoil productivity losses adversely impacting food production capacity for decades. Alternatively, you can mine 21 tonnes of uranium to produce 2 tonnes of slightly enriched fuel transported in 1 rather small minivan.

It is strongly ironic that the green facet of politics is backing this kind of 100 percent renewable plan. Ironic because this amorphous group grew its support base with a very public concern for the natural world. Our forests, rivers, wild areas and biodiversity. They coupled this with the concern that every rational person has with clean air, water and productive soil. These are core green values and they resonate with many people.

But the renewable system envisaged in the AEMO report violates these values in both letter and spirit. The energy system they have modelled is renewable only by definition, and not in any likely relevant physical sense.

But it’s emphasis on logging, slashing, trucking and general bushland violence makes it a renewable system with plenty of red neck appeal.

But wait, there’s more

As I said above. Climate impacts aren’t just about electricity and it’s important to understand the breadth and scale of our climate impacts.

The Copenhagen Diagnosis estimated that the long term sustainable per capita emission level for 9 billion people in 2050 is about 1 tonne CO2eq. The 100 percent renewable scheme constructed by AEMO won’t get us anywhere near that target. To get close to that target would require far more electricity and deep “whole of industry” switch to electrification where possible and to other technologies where not. The AEMO study (p.14) acknowledged clearly that it wasn’t considering any other switch away from fossil fuels except for electric vehicles as noted.

In addition to our energy emissions, Australia has plenty of non-energy emissions. Consider our latest 2010 greenhouse gas inventory (to UNFCCC). The average over the past 20 years of CO2 generated by the cattle industry turning forest into grass has been 69 million tonnes per year. That single activity generates three times the per person annual sustainable level of CO2 emissions … and that’s before you add the cattle.

So the AEMO study isn’t about a total response to reducing our climate damaging activities to sustainable levels, it only deals with one part of that task. We need to ensure that however we deal with electricity leaves us with sufficient social and economic capacity to solve the rest of the problem. It’s not much use blowing your budget on the foundations and having no money left for the walls of your house.


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By Barry Brook

Barry Brook is an ARC Laureate Fellow and Chair of Environmental Sustainability at the University of Tasmania. He researches global change, ecology and energy.

15 replies on “Log, slash, truck and burn – welcome to renewable electricity nirvana”

[…] Continued exclusion of nuclear will prove costly. It will bring high system costs to ensure reliability of supply from very high levels of intermittent generation. It places large bets on the success of technologies that are commercially nascent and very expensive (such as solar thermal with storage), encountering serious engineering challenges to bring to market at scale (such as hot dry rock geothermal or carbon-capture and storage) or simply a sustainability disaster when scaled up (like giant, brand new biomass industries). […]


[…] Continued exclusion of nuclear will prove costly. It will bring high system costs to ensure reliability of supply from very high levels of intermittent generation. It places large bets on the success of technologies that are commercially nascent and very expensive (such as solar thermal with storage), encountering serious engineering challenges to bring to market at scale (such as hot dry rock geothermal or carbon-capture and storage) or simply a sustainability disaster when scaled up (like giant, brand new biomass industries). […]


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