Southerly: New Zealand Biofuels, Part 1
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Good story David, we tend to overlook firewood as a bio fuel in favour of the oil replacements. The BRANZ HEEP study said something like that another Huntly power station would be needed if all solid fuel heating went electric.
I did notice that George never did get around to saying what the energy yield ratio for the pellets was, other then indirectly saying the inputs for the mill and auger were low. Any firm figures?
The consumer website (premium content) has recent updates of home heating fuel cost comparisons; a pellet fire is about mid range of the options according the them, not among the most cost effective as reported.
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Andrew:
George is still getting back to me on a number for the energy yield ratio (obviously he didn't make it in time for the programme). I'll post an update as soon as I hear back.
In terms of the relative cost of wood pellets, I was going by the published figures I had seen from various studies (although I have not seen the latest 'Consumer Magazine' information) -- as well as information supplied by Scion, as follows:
Several studies have shown that wood pellets are among the cheapest heating options on the New Zealand market
See also this document.
As you'll appreciate, the costs arrived at are partly dependent on the type (and complexity) of the analysis used. For example, do they consider the capital cost of the burner/heater, the cost of compliance with emissions restrictions, maintenance costs (chimney sweeps?), the cost of time spent by the end-user maintaining/fuelling the system; what assumptions do they make about length of operational life, what assumptions do they make about operational climate (obviously the lower mean winter temperatures make a heat-pump much less efficient in Invercargill than in Kaitaia)?
To illustrate: the 'Warm Homes Technical Report' suggests that wood pellet systems are the least expensive household heating method in Christchurch (see this link, Section 19.2, Figure 19.2).
For this reason, I preferred to go with Scion's general statement about wood pellets being "among the cheapest heating options". But I'm certainly happy to be corrected if more up-to-date scientific data has shown Scion's claim to be incorrect.
Are you able to post a brief summary of the 'Consumer Magazine' data and methodology? What do they give as the cost differences between wood pellets and other low(er)-cost forms of heating?
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At my previous house, where I had a potbelly, I used to buy a dark greeny grey cylindrical log, which games in boxes of 6 or 8 from the warehouse. I used them to get things going with the fire before moving onto coal as they caught fire well and left good embers.
Are these a brand of the pellets that are discussed here? Or was that not accidentally good use of biofuels?
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I can't see the methodology for the Consumer results, but it is fuel and not total cost based. Adding in the other factors for a total cost of ownership would give a significantly different result - on this basis heat pumps are more expensive then plain electric panel heaters. Average figures from Consumer (reading of a graph with ranges so a bit rough) was;
pellet burners 11c/kWh
wood burner 8c/kWh
Heat pump 8c/kWh
Panel heater 20c/kWhI couldn't see the BRANZ HEEP study, your link was to an MfE report based on a phone survey. The HEEP studies have found significant issues with self reported energy usage, which is why you need to measure everything.
I did see the data for Christchurch - $15/month is very good given one 20kg bag of pellets will heat a home for 28 hours on low and costs around $8.50. That's less then 2 hours heating per day in winter...Kyle: I think those were firelogs, a different thing (and more expensive then pellets)
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Kyle: I think those were firelogs, a different thing (and more expensive then pellets)
Dammit. Apparently not everyone gets a bargain.
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Andrew:
Sorry, I was writing at top speed and somehow pulled the wrong title through from my spreadsheet -- that'll teach me to double-check my links before I post (I've corrected the report name in my original reply).
Yes, as you point out, this does give rather a dramatic illustration of my point about methodology.
I could (and probably should) also have pointed to this report from the University of Otago Wellington School of Medicine and Health Sciences (which compares heat-pumps, gas, and pellet burners).
Lifetime costs (capital plus operating costs) over a 20 year life: pellet burners’ and heat pumps’ overall lifetime costs are almost identical. Gas heaters are the most expensive. A sensitivity analysis shows that if electricity prices were to rise significantly (e.g. by 10%) heat pumps would become more costly than pellet fires. This appears more likely than a rise in pellet prices (or gas prices).
I'm not advocating for wood pellets vs. heat-pumps (or anything else), but I'm just trying to point out that the methodology dramatically affects the results of exact comparisons. Given that some of these studies are more than a bit vague on describing their methodology then this is why I chose to go with Scion's rather more general "among the cheapest heating options" line.
P.S. By the way, are you sure that the lifetime costs of a resistance heater would be less than a heat-pump? We use about 32 kWh per day of heat over the four winter months in our house in CHCH. In round numbers (at an electricity price of, say, $0.15/kWh) that would cost about $6000 over, say, a ten-year lifetime. Given our mean temperatures and the quoted COP of our heat-pump, then it should be able to provide the same amount of heat for around $2500. Since the capital cost of the heat-pump is only about $2000 then it seems to me like I should be well ahead on lifetime costs (just doing the numbers in my head -- it's not an inflation-adjusted calculation, or anything).
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The devil is in the details when it comes to methodology used in studies. But when the proponent of a technology has glowing (pardon the pun) findings and an independant consumer advocate has another view then I start to get sceptical.
The cost comparison of panel heater and heat pumps is from this BRANZ report from the DBH review of energy efficiency in buildings. See section 9 page 23 which details the cheapest option for a given heating energy use. It looks like you use about 4,000 kWh in winter, so say 5,000 per year and this is below the change over point even at 5% discount rate. Average heating energy in NZ homes is about 3,900 kWh pa (fromm HEEEP year section 3.3).
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Please excuse my spelling, I'm an engineer.
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Andrew:
This is drifting away from the topic of this discussion, but BRANZ seems to pull through some quite strange assumptions from their thermal modelling results.
For example, BRANZ seems to assume that you need two heat-pumps worth $5000 (in total) for a house like mine. In reality, I have a single $2000 heat-pump.
Unless I'm reading this table wrong, then it certainly doesn't apply to my heating situation, and (I doubt) that of many people in this country. Maybe they're using old pricing figures?
But using their energy pricing and discount assumptions for my $2000 heat-pump: I get a total present value of $8218 for capital + energy costs, compared to $11,584 for a resistance heater over 25 years. I make $3366 (yay for me!) -- but, more importantly, I help stop the country from building another Huntly power station or two...
RE:
The devil is in the details when it comes to methodology used in studies. But when the proponent of a technology has glowing (pardon the pun) findings and an independent consumer advocate has another view then I start to get sceptical.
I know what you're saying here, Andrew. But I don't think there's a conspiracy between a "glowing finding" from Scion and "another view" from 'Consumer Magazine'. In my opinion, "among the cheapest heating options" is still a fair description of the situation -- particularly when you consider the range of possible operating conditions (e.g. heat-pump in Invercargill vs. wood pellet burner running under an optimum control regime). However, I would certainly agree that from the studies I've seen you couldn't describe the wood pellet burner as the cheapest heating option (although it's still a hell of a lot cheaper than some other options, e.g. an open fire).
But thanks for the debate -- it reminds me of being back at engineering school! Perhaps what this highlights is the lack of a comprehensive and rigorous study of this issue. It would also be interesting to see some numbers on public good vs. private good in terms of heating systems.
P.S. Spelling excused!
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But do you use your heat pump in reverse in summer to cool the place down? If so, there's another stack of power use from the pump, while the heater is tucked away in the cupboard for the season. OTOH, how much power does my ceiling fan use?
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Great post again, David.
Just throught that I would point out that energy yield ratio is often referred to as EROEI (energy return on energy invested).
[**REPLY:** Thanks, Stephen. I'm kind of randomly bilingual between EYR & EROEI. There's probably some rule about which one to use in a given situation (US vs. UK?) but I've never been able to figure out what it is -- DH]
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Saw dust would otherwise be used in the garden product industry where it will emit its carbon at a reduced rate.
Dunno about that. I used to develop and install software in plants that cut up panels of wood for furniture. All the sawdust was burnt off on site. Usually the heat produced was used for...nothing. I expect a lot of that still goes on.
Still, I can die happy in the knowledge that we helped preserve native forests by getting the very best fitting cuts out of those panels :-)
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A prob of biomass is that the concerntration of pollution in an urban area will degrade air quality in winter months - especially in Christchurch.
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I think the idea of wood pellets is that, unlike any old hunk of wood, the fuel is quality assured. And apparently the pellets have a very low particulate emission level. Whether this makes them ok for mass usage in Christchurch, I assume David hass already sussed this out?
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All the pellet fires are emissions compliant, if you can control the fuel supply and fire design you've pretty much got the air quality problem solved. There was some problems with wood (log) burners operating on low output and people 'de-tuning' their fires, resulting in more particulates produced; but I think the pellet fires had solved this one.
Stephen Crawford raised a good point about the when waste products (like fish and chip oil) become commodities in their own right - your 'free' fuel becomes subject to supply and demand. Might not be an issue with the amount of waste wood we produce here not. But when we start to see wood fired central heating, process heat and co-gen then supply might start to get squeezed.
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All pollution is compliant until ruled otherwise.
The arguement for compliance over best practise will lead to disaster at a slightly slower rate.Stevens point of new markets for once 'free' goods brings up that Canty Elephant we all ignore. Free water for irrigation, exported as milk to the world and leaving a stinking shrivilling mess behind.
Rural infrastructure paid for from water may be one answer. If the practise is nolonger feasible in Canty after than - oh dear, how sad, never mind. -
All pollution is compliant until ruled otherwise.
Cute soundbite, but there are urban emission standards for domestic wood burners now.
Why can't compliance and best practice be the same thing? And veering back on topic, what part of the pellets will lead to disaster? -
Canty air kills.
Hidden in the bowls of ecans website (yes I can't find it right now) is a health report stating 1% of deaths and 3-5% hospitalisations of people in winter months are directly attributed to Christchurch air pollution .
We need to start from zero particles and I'm sure our communal obsession with cars will fill any remainder.
Dear old Windington doesn't have this prob - Go Makara! -
Canty air kills.
this is an argument to ban all dodgy emissions. cars, trucks, buses, fireplaces, etc.
it is not an argument against wood pellets. -
The various links claim pellets are the cheapest heat.
This is just fraud.
74% of woodburners & 52% of open fires use free stuff.
(cheers for the link David)As good as pellets might be, they're still omitting particles and a conversion to pellets will be expensive and only delay the inevitable.
Lets skip ahead to electricity and put the fires out in christchurch.
PV for the houses and make them mandatory in rented accom. -
they're still omitting particles
so CHC is gonna ban petrol and diesel vehicles?
Now we're talking! -
Ancient brewery discovered on mountaintop in Peru:
. . . hot-burning llama and guinea pig dung, along with other refuse from the settlement, were used to boil water and other ingredients . . .
http://www.speroforum.com/site/article.asp?idCategory=24&idarticle=829
Where's Riddley when you need him, dammit?
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Michael, from your arguments it sounds like we should ban free firewood - its obviously a huge source of particulates, after that we can work on the vehicles.
As for switching to electrity, please tell me where it is going to come from and how you are going to get it into Christchurch?
PV for the houses? Be cheaper to burn money in the fireplaces...
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What price a life?
PV is the logical step for that pocket between the Alps and the Port Hills. It may well require huge assistance to get there but the true cost isn't being counted yet.
Once air quality, hospitalisations, and death are added to the costs PV will become the clear alternative.
Certainly those blessed with wind resources go for the pelletts.
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Just comment on biofuels in general and not pellets in particular.
A huge amount of plant molecular biology is funded by the DOE in the US. Specifically to develop plants as alternative energy sources. Setting aside for the moment the corruption that has led to the use of corn as an energy source. A lot of pretty neat work has been done on designing the perfect energy crop. Things like lignans which are so useful for binding pellets together actually make it really difficult to get energy out of a crop.
The research isn't there yet but my impression is that we are not very far away from a purpose engineered crop purely for energy production.
As far as I can tell the key to making it viable is to avoid trying to transport small amounts of the energy eg turning it into ethanol and moving it around the country to stick into cars. If you want to get the best from a biofuel you build a generator to convert the biofuel into electricity at the site of production.
As an aside I've always thought there must be a way of getting plants to produce hydrogen directly. It would involve some interesting biochemistry and some interesting engineering. Of course compressing the hydrogen would probably lose it's value but I like the idea of burning hydrogen instead of carbon.
The point is plant biology will be the answer :). They are after all the most efficient solar energy converters.
cheers
Bart
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