Southerly by David Haywood
15

Energy Special, Part 1: What is Energy, Anyway?

This is a transcript of an episode of Public Address Science which was originally broadcast on Radio Live, 25th August 2007, 5 pm - 6 pm.

You can listen to the original audio version of the programme by clicking on the 'Play the audio for this post' link at the top of this page or the 'Audio' button at the bottom of this page.


* * *

Background:

[Sound of thunderstorm]

Voiceover:

Unless we're experiencing a thunder and lightning storm like this one -- where colossal amounts of electricity are discharged into the air above us -- the subject of energy is something that most of us rarely think about. In our normal day-to-day lives, we simply assume that, for example, energy in the form of petrol will always be there to fill the fuel tank in our cars, and that energy in the form of electricity will flow from the wall-sockets in our houses at the flick of a switch.

But over the next few months I'm going to examine the subject of energy in a lot more detail. Where it comes from, how it's used, and -- at the risk of sounding overdramatic -- its vital importance to civilization as we know it.

I'll be looking at the ways in which energy has transformed human life throughout history from the Palaeolithic to the space age -- and I'll be talking to energy economists and international energy experts about the importance of energy to global society.

Then in the last half of the series, I'll narrow my focus to New Zealand. I'll look at our energy resources and consumption, and I'll talk to New Zealanders in the energy sector as well as our government policy makers. Finally, I'll attempt to look into the future, and find out what we should be doing as a country to meet the energy challenges of the next few decades.

Background:

[Wind over high-tension power lines]

Voiceover:

When you really think about it, it's humankind's ability to capture and harness energy -- over and above the simple food energy that all organisms obtain -- that actually makes human beings what we are.

Our ability to capture this non-food energy impinges upon

all aspects of our existence. For example, captured energy was required to manufacture every article of clothing that you're wearing right now. Captured energy was required to fertilize, harvest, transport, or refrigerate virtually every item of food that you've ever tasted. And captured energy was required to manufacture every implement or tool that you've ever used: from knives and forks, to screwdrivers, to alarm clocks, to the roof over your head.

Captured energy is, quite literally, the lifeblood of civilization: without energy the cars and buses don't run, water doesn't come out of the taps, and our high-tech hospitals become nothing more than unrefrigerated mortuaries... without captured energy humankind is back in the stone-age. In fact, we're back in the really bad bit of the stone age -- the bit before fire was even discovered.

But what exactly is energy?

It's actually surprisingly hard to define. Before we think about energy, we've got to talk about something called 'work'.

Background:

[Sound of block and tackle]

Voiceover:

I'm using an old-fashioned block-and-tackle to lift some sacks of cement about two metres up into the air. In the normal sense of the word, I'm finding it to be hard work. But the word 'work' also has a specialized scientific definition. In a scientific sense, work is performed when a force is applied to an object -- and that object undergoes movement. This 'scientific' work, measured in joules, is simply the force acting on the object multiplied by the amount of displacement that it causes.

In my particular case, I'm applying a force to the sacks of cement (via a rope) in order to overcome the earth's gravitational pull. The mass of the cement is 100 kilograms, and therefore it weighs about 1,000 newtons under the earth's gravitational field. So when my arms

apply 1,000 newtons of force to lift the sacks of cement two metres into the air, then I've performed 2,000 joules of work (i.e. 1,000 newtons x 2 metres = 2,000 joules).

Now work is important because it's the way we see what energy actually does. Energy itself is rather intangible, and so -- in scientific terms -- energy is most often defined simply as:

Energy is the ability to do work.

So let's get back to my sacks of cement. If a normal person were to look at me, they would simply see a sweaty geezer hauling on a rope. But to the eyes of a scientist, I'm doing 2000 joules of work in lifting the sacks of cement -- which tells them that 2,000 joules of energy must be flowing in a Harry-Potter-like manner from my fingers to the rope.

Background:

[Sound of wind turbine]

Voiceover:

Of course, energy can take many different forms. It could, for example, be kinetic energy contained in a quantity of air, which moves rapidly through a wind turbine like this one, and performs work on the rotor blades.

Background:

[Sound of water running down the spillway of a dam]

Voiceover:

Or it could be the gravitational potential energy contained in a quantity of water sitting in a dam, which can be allowed to fall under the earth's gravity, and perform work on a water-turbine.

Background:

[Sound of car engine]

Voiceover:

Or it could be the chemical energy contained in a fuel such as petrol, which is converted to thermal energy (or heat) when it burns and expands the air inside a cylinder, so that work is performed on a piston.

Background:

[Sound of electric motor]

Voiceover:

Or it could even be electrical energy, which flows through coils to induce a magnetic field, and performs work on the rotor of an electric motor.

But in terms of the way we generally use energy in society, it's not just quantity that's important, but also the rate with which energy can be turned into work. The amount of work done per unit time is called power, and it's measured in watts -- where one watt is equal to one joule of work done every second.

* * *

And to prove that no effort has been spared in bringing you this programme, I've just climbed all the way up the staircase in Auckland's Skytower building. Along the way I've been measuring both my work and my power output.

It's taken me 14 minutes to raise my 85 kilogram body up 234 vertical metres of staircase, which equates to 195,000 joules of work performed. I'm feeling really quite tired, but that's only about the same amount of energy as contained in just seven millilitres of petrol (around one cent's worth at current prices).

I started my climb running up the stairs at the bottom with a power output of just over 1,000 watts (1,000 joules every second). But I just finished my climb at a slow walk and a power output of only 200 watts. My average power output during the whole climb was a mere 227 watts.



Above: Work and power output when climbing Skytower (a)–(b) running up stairs, (b)–(i) walking up stairs, (i)–(j) running up last three flights of stairs, (c) breathing heavily, (d) legs beginning to feel tired, (e) beginning to perspire heavily, (f) perspiration dripping from chin, (g) legs extremely tired and perspiration dripping from end of nose, (h) legs starting to hurt, (i) shirt soaked with perspiration, (j) reach the top of the stairs (63rd floor) [click to see a larger image].

To put that into perspective, the power output of a 50 cc motor scooter is around 2,000 watts, the power output of a medium-sized car is around 100,000 watts, and the power output of the engines on a Boeing 747-400 aircraft is more than 140,000,000 watts.

Background:

[Sound of Boeing 747-400 aircraft]
[Sound of sticks rubbing together]

Voiceover:

Those numbers are rather overwhelming, but now that we have an understanding of basic

concepts such as work and power we can begin to discuss the subject of energy in more depth.

I'm making a start by using my relatively meagre human power output to make fire -- literally by rubbing two sticks together. And I'm not having much luck, although I've just managed to get a bit of smoke.

But more on that next week: when we go back to the dawn of time, and look at the way energy has been used throughout the course of human history.

Background:

[Sound of sticks rubbing together]

* * *
Further information on this episode:

1

The Pivotal Engine

This is a transcript of an episode of Public Address Science which was originally broadcast on Radio Live, 4th August 2007, 5 pm - 6 pm.

You can listen to the original audio version of the programme by clicking on the 'Play the audio for this post' link at the top of this page or the 'Audio' button at the bottom of this page.


* * *

Theme music...

Background:

[Sound of engine starting]

Voiceover:

That's the sound of the pivotal engine: a radical new two-stroke engine design from a sub-division of Mace Engineering -- one of Christchurch's largest companies.

Now when you think about two-stroke engines (if you think about them at all) you'll no doubt think about the type of motors you find on cheap lawnmowers and chainsaws: low cost, but also low efficiency, short lifetime, and very high exhaust emissions.

But two-stroke engines do have an important advantage over their more environmentally-friendly four-stroke big brothers. This is because they have a power stroke once every engine revolution -- rather than once every two engine revolutions as with a four-stroke motor -- and therefore have approximately twice the power-to-weight ratio.

And it is this improved power density that has seen a number of automotive engine manufacturers conducting research into two-stroke motors over the last couple of years.

A two-stroke engine with the environmental features of a four-stroke could significantly improve overall vehicle performance. But the Christchurch engineers working on the Pivotal engine have a big head-start on practically everyone else. They've been developing their engine at full throttle for over a decade.

* * *

Interviewer:

I'm now sitting in the office of Paul McLachlan, the inventor of the Pivotal Engine. Can you explain how -- in terms of its basic design -- the Pivotal Engine differs from a conventional two-stroke motor?

Paul McLachlan:

We set out to overcome what are the inherent shortcomings of a conventional two-stroke engine. [In such motors] you have a sliding piston, restrained by a cylinder -- and in that cylinder you're cutting the ports for the engine to breathe, i.e. the transfer ports, and the exhaust port.

[This] causes a number of difficulties. We've overcome these by designing the engine to have a piston which is restrained by a pivot bearing, [but which] still has a connecting rod down to a crankshaft in a conventional way.

[Restraining the piston] allows us to take the load off the surface of the chamber. [This] means that we don't have to lubricate the piston as a sliding piston, and it also means that we have a pivot point on the piston -- which allows us to run water into the piston itself and back out the other side via the pivot.

So it becomes a water-cooled piston. And so we have a water-cooled engine with a water-cooled piston, and that overcomes all of the inherent shortcomings of a two-stroke engine that stops you using it [for example] in your car.

Interviewer:

So I guess a way of explaining it would be to say that in a conventional two-stroke motor you have a cylindrical piston inside a cylindrical cylinder (as it were) sliding up and down.

But in your pivotal engine, the piston is more like a flapper. So seen from the top the 'cylinder' would be square in profile, and seen from the side the piston would be moving up and down

-- and tracing out a shape a bit like a Chesdale cheese segment.

[click here to see an animation of the Pivotal Engine].

Paul McLachlan:

Yes, and we're using only the outer part of the cheese segment. So it moves through about a 36 degree radial angle.

Interviewer:

So when you talked about the problems with conventional two-stroke motors -- why they're not used in a normal automotive situation -- I guess you could summarize the problems by saying: low thermal efficiency, short operational life, poor emissions (particularly in terms of oil residue in the exhaust).

How does the Pivotal Engine deal with those issues -- what improvements have you been able to make?

Paul McLachlan:

We'll start with longevity. The problems with a two-stroke engine [in terms of longevity] is that if you're wanting to get the high-performance benefits of a two-stroke engine, then you end up with quite sizable ports. Therefore what you've done is taken away a lot of the physical support for your piston by taking sections out of the cylinder wall.

[But this] also has the effect of reducing the amount of contact which would take heat out of your piston. So we overcome the restraining by the fact that it's held by bearings; and the heat by the fact that we're internally water-cooling the piston.

The emissions are really a matter of two things. There's the lost unburnt fuel with a normal [carburetted] two-stroke -- whereby you lose [fuel] out the exhaust totally unburnt. This decreases the efficiency of the engine, but also results in a very unacceptable level of hydrocarbon emissions.

Now that gets overcome in any two-stroke engine to a very high degree by having a direct injection system -- which means to say you're injecting the fuel from the top of

the head, and only after you've closed the exhaust ports, so that you're not losing any of that fuel.

The other [source of] hydrocarbons is the oil you use to lubricate the piston. We overcome that by the fact that the piston is now not actually in contact with the surface of the chamber, and therefore we only need a very small amount of oil [which is directed to] the compression seals.

Interviewer:

So how much oil does the Pivotal Engine use in comparison to a conventional two-stroke?

Paul McLachlan:

At this stage we would say that it's around about a tenth of the amount of oil that you would use in a modern direct-injected type of two-stroke engine.

Interviewer:

... and normally you'd say they use about ten times the amount of oil of a good four-stroke -- so you're using about the same amount of oil?

Paul McLachlan:

We're getting close to being able to having comparable oil usage to a four-stroke engine. But on top of that, of course, you don't have to have an oil change -- so the overall use of oil is actually slightly lower.

Interviewer:

In which areas do you see the Pivotal Engine first making an entry into the market? You've been going for over a decade now with some pretty intensive R & D -- so I imagine that coming to market is something you're pretty keen on?

Paul McLachlan:

Yes, we have in the last two or three years been focussing very much on a first step into the market place. We [initially looked] at light aircraft, and we have a lot of interest from that point of view, but there were various reasons why we decided on a generator product -- we have a good partner in the US for

a military generator, and that's our main focus at the moment.

The potential there, of course, is based on its power density -- and so it's a stand-alone portable generator. We have simulated all of the components that make up the stand-alone generator for using our engine, and we end up with a weight which is about 25 per cent of the weight of a [comparable military] generator. So for many applications that will make it an ideal choice.

And there are a lot of other opportunities once we have this first product as a base engine. Certainly we have a lot of interest in the hydrogen potential. We have full control of all of the thermal surfaces on the combustion chamber, and that's due to the fact that we have the piston cooled independently with its own water cooling.

In hydrogen the big advantage is that we actually can run the engine at a reasonable temperature for good thermal efficiency -- but we can avoid any hot-spots on the piston or in the head, [which is] the limiting factor in trying to run hydrogen in a conventional engine.

We see a vehicle such as a plug-in electric vehicle -- which would be a hybrid with hydrogen as the core range-extender in the vehicle -- and we have a lot of interest in that concept.

Interviewer:

In terms of your initial market niche that you're aiming at -- the generators -- do you have anything like a timeline for when you expect the first production to roll off the line?

Paul McLachlan:

We have component supplier already making the key components. We're hoping to have most of those ready at the beginning of next year to assemble engines that are representative of a series-production engine. They will go into test

with the generators attached at our partner on the generator project -- and also those engines will then get used in some hydrogen development programmes, which we're working on with some European development companies.

* * *
Voiceover:

It's heartening to see that a device as astonishingly simple as the piston-cylinder mechanism in an internal combustion engine can still be improved by a cunning engineer. The ingenious Pivotal engine avoids the efficiency, longevity, and emissions problems that plague conventional two-stoke motors, while still delivering a mind-bending power density at low cost.

Its debut as a military generator will be closely watched, and it will be interesting to see where it ends up being used in the future.


Theme music...

* * *
Further information on the Pivotal Engine:

A Brief Look At Forensic Linguistics

This episode of Public Address Science was originally broadcast on Radio Live, 9th June 2007, 2 pm - 3 pm.

You can listen to the programme by clicking on the 'Play the audio for this post' link at the top of this page or the 'Audio' button at the bottom of this page.

Further information on forensic linguistics:

11

New Zealand Biofuels, Part 2

This is a transcript of an episode of Public Address Science which was originally broadcast on Radio Live, 2nd June 2007, 2 pm - 3 pm.

You can listen to the original audio version of the programme by clicking on the 'Play the audio for this post' link at the top of this page or the 'Audio' button at the bottom of this page.


* * *

Theme music...

Voiceover:

I fully admit that a few years ago I was something of a biofuels sceptic when it came to the replacement of automotive fuels in New Zealand. Since then, however, things have changed dramatically. The price of fossil fuels has risen enormously (a trend which is expected to continue), and new technology has come onto the scene which promises cheaper and less energy-intensive biofuels processing.

Recently, two New Zealand Crown Research Institutes -- Scion and AgResearch -- have joined forces with US enzyme manufacturer Diversa to work on automotive-type biofuels. Despite the criticisms levelled at some overseas schemes -- in terms of low energy yield ratio (and consequently high cost), as well as concerns over long-term sustainability -- the New Zealand consortium believes it has the answer to sustainable biofuels for this country.

I talked to Dr Trevor Stuthridge at Scion, and began by asking him to describe the feedstock and manufacturing process for their proposed biofuel scheme.

Dr Trevor Stuthridge

Our starting point is to ask: is it possible for New Zealand to convert one of its pulp-and-paper mills over to an ethanol facility?

So we're looking to use wood as our feedstock; and wood is quite a complicated material. It has both the cellulose -- which is what most people are using for next generation biofuels -- but it also has hemicellulose, which is another type of sugar polymer, and it has lignin.

The process that we're developing with Diversa is to look at ways of first physically and chemically breaking the wood down into pulp material -- which is where all the glucose that we use for the ethanol production is -- and also releasing the lignin, which we can recover for energy or chemical production, and also recovering the hemicelluloses, which are another

source for making ethanol.

So what we're doing in the first instance is physically and chemically breaking the wood down -- just as they already do in the pulp and paper industry. And then we're using Diversa's unique enzyme cocktails to break polymers [such as] cellulose and hemicellulose into their sugars.

And it's these sugars that we can pass on into another process with another bacteria, or a yeast, that actually ferments it into the ethanol. So in this way we can take a fairly difficult to break down material like wood, and turn it directly into ethanol.

Interviewer

Right, okay. So last week on this programme we also talked about biofuels and looked at the energy yield ratio for corn bioethanol in the US -- which is absolutely terrible -- only just over 1. Do you have a figure for the energy yield ratio for wood bioethanol using the Diversa process on this sort of large scale?

Dr Trevor Stuthridge

We're still working on that, so I don't have numbers at hand yet. In fact, we're going through that exercise at the moment as part of our feasibility study. But certainly our belief is that the energy yield ratio is favourable for lingo-cellulosics -- particularly derived from forestry resources. Management costs for the crop are rather lower (in our opinion), compared to food crops like corn, and the yield per hectare can be rather higher.

Interviewer

Now you've mentioned food crops -- and, of course, one of the criticisms of bioethanol in other countries is that it displaces food crops. Presumably this isn't a criticism that could be levelled at your scheme for biofuel manufacture?

Dr Trevor Stuthridge

We see this as a key advantage of what we're proposing, because much of the lands that the forests are growing

on are non-food quality. They're not suitable for food crops.

Certainly this is a key constraint in the United States, where the price of corn has now doubled because of ethanol initiatives. In some states up to half of the corn is being used for ethanol production, and that's starting to impact things like food prices and beef prices.

We think by targeting a non-food crop, and using essentially non-food quality land, we have a significant advantage. And certainly in New Zealand, from an international perspective, that's a key advantage to this country in our opinion.

Interviewer

That's reassuring. But another criticism of biofuels -- certainly in the US and Europe -- is that it takes a huge amount of land to produce just a fraction of the country's fuel requirements. Using your proposed method how much biofuel could feasibly be produced in New Zealand?

Dr Trevor Stuthridge

Our estimate is that a single pulp-and-paper mill facility could produce over 200 million litres per year -- and that would be quite sufficient to take us beyond E15 [i.e. a mix of 15 per cent ethanol, and 85 per cent petrol] in terms of fuel substitution.

In reality, if we took all of the forestry crops and the trees that we're exporting overseas -- it appears even possible that we could completely substitute in the long term. But, of course, there would be a significant capital investment required to process that sort of material.

Interviewer

Okay, right. But wouldn't there also be a massive cost incurred in terms of lost revenue from the wood feedstock that could otherwise have been exported as timber?

Dr Trevor Stuthridge

That's an interesting question and one that we're [considering] at the moment in our feasibility study -- because whilst at times wood and pulp can

be very financially positive, there are [also] times when it's non-profitable. So you get lots of ups-and-downs in that market.

With ethanol we believe we'll have a much steadier market -- so on average it's quite possible that ethanol production could even be better economically than current use of the forest resource.

Interviewer

You've pointed out that producing biofuels from New Zealand forests is no less sustainable than producing timber. But actually how sustainable is timber production in reality? Can the land keep on producing indefinitely?

Dr Trevor Stuthridge

[I think that] over the years the forestry industry and the wood-processing industry, have developed very good management strategies for the production of the wood stock, and the harvesting and replanting.

[So] this is still a pretty sustainable option for New Zealand in terms of land use -- we're not substituting for high-value land. I think management practices for forestry are pretty good in this country, from what I can tell.

Interviewer

I guess this is the $64,000 question -- but do you, at this stage, have any feel for the cost comparison to current petrol prices?

Dr Trevor Stuthridge

We don't have a strong feel for that yet. I think the challenge for ethanol at the moment is that in many parts of the world it's still heavily subsidized, and the price is still well above petrol.

The key challenge for ethanol in terms of cost of production is the enzymes -- and that's why our relationship with Diversa is critical to this initiative. I guess overall our aim would be to get the cost of ethanol being equivalent to petrol. We don't believe, as in many other parts of the world, that asking the consumer to pay more for their fuel is likely to be particularly well taken up.



I think New Zealand still has an opportunity to be a leader in this field, whether it's with pulp and paper or forestry or other crops. We're in a position geographically where being self-sufficient is probably the best option for us.

* * *
Voiceover:

While it's perhaps a little too early to declare 'mission accomplished' on the transport energy front, the proposed New Zealand bioethanol scheme seems to overcome many of the objections that are made against overseas biofuel manufacture.

Given the scope for improvement in the fuel efficiency of New Zealand's vehicle fleet, sustainable biofuels could -- even in the medium term -- have a dramatic impact on our energy supplies. And, even if not completely perfect, they may well be a much better option than our current dependence on fossil fuels for transportation.

Theme music...

* * *
Further information on biofuels:

29

New Zealand Biofuels, Part 1

This is a transcript of an episode of Public Address Science which was originally broadcast on Radio Live, 26th May 2007, 2 pm - 3 pm.

You can listen to the original audio version of the programme by clicking on the 'Play the audio for this post' link at the top of this page or the 'Audio' button at the bottom of this page.


* * *

Theme music...

Voiceover:

There's been a lot of talk about biofuels recently, but what exactly are they? Well, essentially they're the end product of nature's own solar collector. Plants absorb energy from sunlight, and then store this energy by turning water and carbon dioxide into hydrocarbons. By employing an appropriate chemical process, such as burning these hydrocarbons, the original solar energy can be re-released in a concentrated form that we can use.

The neat thing, of course, is that burning these plant-derived hydrocarbons only releases the same amount of carbon dioxide as the plants themselves absorbed from the atmosphere in the first place. So, from this perspective, biofuels can be said to be carbon neutral, because it's theoretically possible to manufacture and use them without adding to the overall amount of carbon dioxide in the atmosphere.

However there is, admittedly, a potential problem. Because the energy in raw biomass isn't necessarily in a form that can be easily used -- then additional energy is required to harvest the biomass and process it into a usable form. Not to mention the energy input that's also required in terms of planting, tending, and fertilizing a biofuel crop.

This leads to something called the energy yield ratio. In simple terms, this is the ratio of the chemical potential energy stored within the fuel, in comparison to all the energy input required to bring the fuel to the point of end use. The higher the energy yield ratio, the more energy you get out of the fuel in comparison to the energy input required during processing.

Some biofuel crops (notably bioethanol from corn in the United States) have an energy yield ratio which is only slightly greater than one -- in other words: absolutely pitiful. But it's important to realize that this is by

no means the case for all biofuels. And it's certainly not the case for biofuels in this country.

You might be surprised to discover that (according to the Energy Efficiency Conservation Authority) in New Zealand we already get nearly ten per cent of our total energy input from biofuels -- in the form of the burning of firewood and waste biomass in households and industry. Now, of course, this doesn't translate to ten per cent usable energy output because -- for various reasons -- biofuels are currently consumed in a rather inefficient manner [in 2006, a publication from the National Centre for Climate–Energy Solutions stated that "bioenergy currently provides about 5% of New Zealand’s total primary energy supply"].

But if we could economically make use of more biofuels for simple purposes, such as household and industrial heating, then it would have two important results. Firstly, it would displace the consumption of some of the fossil fuels which are currently used for this purpose; and, secondly, it would displace consumption of electricity used for heating -- thus freeing up both electrical energy and our electrical networks for other purposes.

It turns out that an interesting and relatively new manufactured biofuel could help us achieve just that. Wood pellets have been on the market for a few years now, and have the potential to become an important part of New Zealand's energy mix.

I talked to George Estcourt, a scientist at Scion (one of New Zealand's Crown Research Institutes) who studies the production of wood pellets in New Zealand. According to Scion's research, wood pellets are among the most cost-effective form of heating in New Zealand -- far cheaper than coal, electrical resistance heating, or gas. I asked George if wood pellet biofuels have any other advantages to offer.

George Estcourt

Yes,

the wood pellet stove is basically designed around the wood pellet. The problem with the normal log fireplaces is that they're tested (to reach their standards of, say, how many grams particulate per kilogram of wood, and that type of thing) [in a] lab using the absolutely correct firewood, moisture content, and so forth.

But as soon as you take it home, and put it in your house, and then you start using a bit of this, a bit of pine, a bit of tea-tree -- and you really don't know what the moisture content is -- your emissions can be ten times [or] a hundred times worse than what they were in the lab. But with your pellet stove, really nothing is going to change, so you're always going to [achieve] high quality results.

The wood pellets themselves are pure wood, which means that there's no other material in there that could cause poor emissions. And [of course] the other thing -- when you get contaminants -- they generally become ash. Anything that can't be burnt ends up in your ashtray. Wood pellets have an ash content of [only] around 0.5 per cent

Interviewer

Right -- and, of course, in the sort of systems you're talking about, the wood pellets are stored in a hopper, and then they're automatically fed through into the combustion space as required. So it's also much more convenient than a conventional log-burner.

Now I think there's a few myths around about the inclusion of dangerous chemicals in wood pellets. Would you mind giving a description of how wood pellets are made, and telling us what they're actually made from?

George Estcourt

The two main feedstocks for wood pellets are either wet sawdust or dry shavings. [The] wet sawdust comes straight off the sawmill bench.

Dry shavings [are] produced once you've sawn [and] dried your timber, and then you're basically dressing the timber to put the nice smooth surface on it. The shavings [that] come off are [a] waste product, and one of the best materials to make wood pellets.

The wood waste -- such as the sawdust and the wood shavings -- have to go through a hammer-mill, and that breaks the material down to a very fine particle size. [If] the material [is] not already dry, like the dry shavings, it will have to be dried. Wet sawdust is about 50 percent moisture content -- [so] you need to drive all that water off and get it down to about 10 per cent moisture content.

Once it's all down at that 10 per cent then it goes through a pelletizer, and this is when the hammer-milled product, which is a very fine-looking sawdust, is pushed through a die. So you're pushing the material through the die, it's heating up, the lignin that's within the wood-fibre softens -- and I think the wood pellet gets up to about 90 or 80 degrees Celsius while it's being formed -- and that lignin holds the wood material together as it's cooling down.

It's a natural glue that's within the wood fibre. There's no additives -- it's pure 100 per cent sawdust or dry shavings.

Interviewer

Okay, so just to recap: the wood pellets are made from waste sawdust and waste wood shavings, and they're held together by a natural glue that already exists within the wood itself.

Now because the wood pellets are made from waste products they'll inherently have a very high energy yield ratio. Have you actually calculated or measured it?

George Estcourt

Obviously when you're producing it from a dry shaving, the only

energy that you're really using is the electric motor doing the hammer-milling and running the pelletizer itself, so there's very little energy required.

We have people having to dry the sawdust [as well]. One of them was using gas to dry the sawdust. [But] he's [now had] a wood pellet furnace made big enough, so that he's actually burning his own wood pellets to dry the sawdust material. [So he is] using a product that [he has] produced [himself]. [He's] not using fossil fuels any more -- so again it would have quite a high [energy yield] ratio.

Interviewer

At the moment, as you've said, the pellets are made from waste wood. But what happens once your market grows larger than the waste wood supply, and you have to use virgin sources? Does the price go through the roof at that point?

George Estcourt

At the moment there is an abundance of sawdust in the North Island. We think that the industry could [increase] maybe ten-fold before you'd have to think about actually growing crops to make wood-pellets.

What we're hoping [and] trying to encourage [is] more processing of New Zealand logs within New Zealand -- rather than just exporting them. And if you can encourage more processing in New Zealand, and keeping the logs here, then we get more sawdust and wood waste [to turn into pellets]. So there's a double benefit if you try [to] get more processing done in New Zealand.

Interviewer

Right, which all sounds very good.

Now, exotic wood crops are -- so we're told -- produced very sustainably in New Zealand. Do you think it would be important to have legislative controls on any biofuel imports to ensure that they've also been produced in an equally sustainable manner?

George Estcourt

I think it would

be helpful to have limitations on what we bring in. [But] on the wood pellet side I can't see that ever happening. We get a lot of emails from companies -- mainly in Europe -- wanting to know if we can export wood pellets to them.

So I think there is [a greater] possibility that we will be exporting our biofuels out of New Zealand.

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Voiceover:

So a simple manufactured biofuel like wood pellets -- which makes use of sawdust and shavings that would otherwise be discarded -- will provide clean and efficient heating in domestic or industrial situations, and could make an increasingly important contribution to New Zealand's energy mix.

Next week we look at another big biofuel that could also be manufactured from New Zealand's exotic forests.

Theme music...

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Further information on biofuels:

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