More Carbon for Soils More Carbon for Crops - Carbon Negative Farming with Bio Char

Beyond Zero Emissions interviews Dr Lukas Van Zwieten, senior research scientist at the NSW Department of Primary Industries (DPI). He's working hand-on in soil research focusing on Bio Char (Terra Preta de Indio / Agri Char)

Lukas Van Zwieten podcast

download

Transcript

Scott Bilby: We've covered the subject of Terra Preta soils in the Amazon on previous shows. For those listeners that haven't heard about it you can learn more from our podcasts on our website at beyondzeroemissions.org. You can look for the interviews that we've done with Johannes Lehman of Cornell University and Adriana Downie of Best Energies. Lukas, can you start by briefly explaining how we get biochar from pyrolysis.

Lukas Van Zwieten: Biochar is a byproduct of a process called slow pyrolysis. Slow pyrolysis is a technology for waste minimisation. It reduces landfill burden of green waste or agricultural waste or forestry byproduct, and it converts that byproduct into energy; either thermal energy or electricity. Then what we are left with at the end of the process is biochar. The biochar is a very high carbon material. We're looking at around about fifty or sixty percent carbon in that material. And the remainder is made up of an ash component. And I guess one of the things that we've noticed is that not all chars are the same. They're all very different beasts.

Scott Bilby: And you've found this out from the field trials you're currently doing at the moment?

Lukas Van Zwieten: Exactly. We've got a range of field trials in operation. We've also done quite a number of pot trials. And also just characterisation of the biochar. We've had a look at fifteen different types of biochars and we've selected about five different sorts to go ahead with field trials.

Scott Bilby: So what sort of field tests are you doing at the moment?

Lukas Van Zwieten: We've got a couple of very large field trials - well I guess they're large with regards to other work done on biochar. We've got a field trial up in the Tweed Valley in sugar cane where we've used biochar made from paper mill waste and we've also made biochar from council green waste.

And that field trial will be measuring benefits to soil health, benefits to reduced greenhouse gas emissions from soil and also improved yield and quality of the cane.

Scott Bilby: Ok, and you're doing some biochar trials at the moment on a corn plot. So how is that going?

Lukas Van Zwieten: We actually harvested that plot this week and we've seen some amazing differences. Its a bit early to give you the exact data at this point in time, but we've seen probably double the biomass production and double the sweet corn yield where we've had high rates of biochar application in the soil. That's somewhere between 10 and 20 tonnes per hectare of biochar. And, yeah, we've had some very, very significant differences in corn production there.

We've also had a look at nutrient analysis in the leaf content, and again different biochars acting in the soil. I guess it's an interaction between the plants and the soil, but we're getting a very different uptake of nutrients into the leaf material when we have biochar present. And we're also seeing differences in greenhouse gas emissions from the soil.

Scott Bilby: Can you tell us a little about the levels of biochar added to the soil - do they replace nitrogen-based fertilisers?

Lukas Van Zwieten: It all depends on the feedstock for the biochar and the processing conditions. For example, some of the biochars we've tested have absolutely no nitrogen in them whatsoever, and no phosphorous, and they are very very high in carbon. Other biochars have a fairly large amount of available phosphorous, and that could quite happily replace a phosphorous fertiliser regime. Some of the biochars also have small amounts of available nitrogen.

Again, it all depends on the feedstock. So when you've got a very woody feedstock material going through the pyrolyser you're going to end up with a very high carbon biochar but you will have a low mineral content. On the other hand, if you're starting to put manures through there, for example dairy feedlot waste, or chicken litter waste from poultry sheds, you're starting to look at materials where you're getting inputs of nitrogen and phosphorous into the system and a large majority of those nutrients will make their way into the biochar product. So, yes and no. Biochar ain't biochar. Some of the chars certainly can replace nutrient addition, but some of the chars, for example from green waste won't replace nutrient addition. There are some very significant benefits though with adding these high carbon biochars. We've recently published a paper showing that the biochars from the green waste materials interact with fertiliser that you've added; in particularl nitrogen fertiliser, and they actually improve the uptake efficiency of those fertilisers. So by combining fertiliser and biochar could be one of the solutions.

Matthew Wright: In regards to the feed stocks like chicken manure. Now normally that off gases methane and things like that. Does that actually lock that and hold that or does that get flared effectively in the pyrolysis process? Like what happens there - does it knock out those fugitive agricultural emissions that are at source there?

(08:22) Lukas Van Zwieten: Yes, certainly. I guess whenever you have waste materials and they're either composted or landfilled for example you do have a risk of emissions, in particular methane which is a fairly significant greenhouse gas. In the pyrolysis process these feedstock materials are put through the pyrolyser. They are heated to 450 degrees or thereabouts, and in that process gases, in particular hydrogen and methane, are liberated. And they're actually the fuel source that drives the whole process. So those gases are captured. It's a very smart piece of technology to capture those gases. Then they're used to - number one - flare or heat the pyrolyser, because it's an externally heated process. The remainder of the gases are used to generate renewable energy. So the whole process is about generating renewable energy, in particular from waste biomass. And it's about locking up carbon, long-term, in soil.

So the big difference, I guess, between composting or leaving this biomass material in a landfill and pyrolysis is that if you compost say a cubic metre of green waste you'll retain most of that carbon. Initially you have maybe twenty to thirty percent loss of carbon to carbon dioxide initially. But when you apply that to soil a lot of carbon goes, in a very natural carbon cycle, the microbes in soil and normal microbial activity will break that carbon down into carbon dioxide, and within usually five to ten years there won't be very much left in the soil. The carbon, however, from pyrolysis unit, the stabilized black carbon as biochar has been shown to last hundreds, if not thousands of years in the soil. So the process is very very different, and the pyrolysis process stabilises the carbon. You are getting very structured forms of carbon, whereas with the green waste material a lot of the carbon is still as cellulose of lignin or even more available forms of carbon which are biodegradable.

Matthew Wright: In Victoria a very common practice with something like wheat stubble is just to burn it off. Is there much calorific value in the wheat stubble and is there much soil value in that?

Lukas Van Zwieten: By burning off the wheat stubble you're losing - and the process of burning is quite different from the process of pyrolysis. When you burn there is oxygen present. And generally you get a very large proportion of your carbon being liberated as carbon dioxide.
In the pyrolysis process oxygen is excluded and you're generally only getting a fifty percent loss of the carbon initially; and that's to the gases which are making the renewable energy. So burning is quite different to pyrolysis, but in the burning process, say where you have after your harvest and you have your wheat and your stubble, there's not very much carbon remaining in the soil following that process.

Matthew Wright: So, you're not actually adding much value to the soils. But if you do choose pyrolysis with that stubble, which seems like the wise thing to do, rather than just letting all this heat go to waste by burning and potential value, what sort of value is in that, in say wheat, which is a crop which our listeners are very aware of?

Lukas Van Zwieten: Sure. Look, it's going to come down to a life-cycle analysis and on of the costs is going to be taking the, or collecting the wheat stubble. Which might preclude it from being used in the pyrolysis process. So yes, certainly wheat stubble would make an excellent feedstock for a pyrolysis process. However, as it sits in the field it's not a waste product and a full life-cycle assessment needs to be done to determine whether it's worthwhile actually collecting the stubble and bringing it to a processing plant.

Matthew Wright: Well, you're out in the field. Tell listeners a bit about your monitoring process and how you are actually validating the theories around how char can work and add value to our farmers' operations.

Lukas Van Zwieten: Sure. Unfortunately, it's a very expensive process to do the full range of testing that we've been undertaking. When you're applying char to a soil in a field trial, the first thing you want to do is fully characterise the char itself. And that includes quite a range of chemical tests on the char and it also includes a range of biological tests. So, we would test the char to see if it is toxic to earthworms for example; to see if it will inhibit plant germination. Once we are happy that we haven't got a toxic form of char we'd then be looking at pot trials to determine some of the benefits that we might see from that char. That would then help us or certainly guide us in understanding how we'd run a field trial.

In the pot trial we would look at changes to soil chemical characteristics, for example, available nitrogen, available phosphorous. You'd be looking at changes to pH, water holding capacity in the soil, changes to biomass carbon for example, changes to the carbon profile, and we're doing that carbon profiling by a technique called pyrolysis GC Mass Spec and that's also helping us to understand if there are any toxic components in char. Ans we certainly have seen quite a few toxic chars. These toxic chars tend to be made in uncontrolled processes. Whereas in the slow pyrolysis process it's a very stable, highly engineered, highly controlled process and we know that there aren't any toxic chemicals remaining on the char itself. By these toxic chemicals I mean mainly the wood smoke chemicals. We've all smelt char or charcoal following bushfire or following a BBQ where you've got that acrid woody smell. That very same material can be quite toxic in soils to micro-organisms. However, with the slow pyrolysis process all of those bio-oils that might be remaining on the char surface are effectively volatolised and converted into energy. So, it is very important to fully characterise the char; make sure that what you're adding to the soil is not going to do any harm.

Then you can start looking at the benefits. As I said before the benefits include improved nutrient availability to plants, improved nutrient uptake, retention, and by retention I mean reduced leaching in particular of nitrates and reduced emissions of nitrous oxide. That's one of the key environmental benefits that we've found with some of the biochars in that we've had very, very significant reductions in nitrous oxide emissions from the soil; between five- and ten-fold reductions in nitrous oxide emissions.

Matthew Wright: In regards to the potential toxicity, we've heard the coal industry trying to jump on the bandwagon, and they're doing research into putting coal fly ash into soils. Would that likely present them with a lot of challenges given the extent of heavy metals that's often found in coal fly ash?

Lukas Van Zwieten: Fly ash is a very different material to biochar. In the coal industry they're aiming to get complete combustion of the carbon. So the more carbon they can burn in the presence of oxygen in their boilers, the higher the calorific value of that coal. So their aim is to get rid of all the carbon in the coal. The fly ash is effectively the mineral component left at the end of the process, which will be high in calcium and magnesium oxides and hydroxides and probably quite a range of other minerals.

With the biochar the difference is that we've got between fifty and sixty percent carbon remaining, so it's a very, very structured carbon material. The fly ash will often look like a white material, not unlike cement dust I guess, whereas biochar is a black charcoal material with mineral content in it as well.

So, the two components are very different. Fly ash itself won't have any carbon in it. Certainly won't be of any use for improving soil carbon value. However, there is some really good data out there showing that fly ash can be quite useful for soil ammendments. In particular where you have low mineral content in soil or low pH. Some of these oxides and hydroxides can help raise the pH. They act like an agricultural lime. So there certainly are advantages, in some cases, for adding these fly ashes. However, it's a very different process.

Matthew Wright: So, not at all related to what we're talking about here with biochar?

Lukas Van Zwieten: They're related in that, yes, you're talking about a soil ammendment, but the two materials are chalk and cheese.

Matthew Wright: Yes. Tell us, when you're out in the field, describe to listeners collecting data; how you actually, physically, go out there and monitor these pipes that are hanging out of the ground and whether they're ten meters apart or one meter apart.

Lukas Van Zwieten: There's a whole heap of things that we do out in the field. I could describe for example the soil testing and the greenhouse gas testing. So, the soil testing we would, in a typical plot, might be 10m by 10m for example, we would go out and we would take four cores from each of those sites and those cores would be up to 40cm in depth and we would then split those cores and the nought to five cm, five to twenty, then below 20cm depth profile. These cores would then be submitted for a range of chemical analyses which would include nitrate and ammonium, nitrogen, available phosphorous. They'd include cat-ion exchange capacity, pH, total carbon, total nitrogen. So, there'd be quite a range of chemical tests done on the soils.

That on itself is not that difficult. But when you multiply that by eighty or one hundred field plots that we're managing then you're looking at quite a large number of sites and comparisons that you're doing. It can be quite and expensive piece of work. So one of our goals is to minimise cost and maximise the amount of information that we're collecting from these field trials and we've got very, very stringent biometrical controls over the treatments and how we do it to make sure that we absolutely maximise the amount of valuable information that we can gain from these trials.

Now, the other aspect that we are doing in the field is greenhouse gas emissions from soil. We are using a technique called static chamber analysis. Effectively, what that means is that we've got a chamber that we take out into the field and we put this on top of the soil and we collect the air on top of the soil. We then collect this air in a special bag, that is a teflon-lined aluminium bag, and we bring that back to the lab and we analyse that air for the greenhouse gases. So, the types of greenhouse gases we are measuring are, in particular, are nitrous oxide, but also carbon dioxide, methane and carbon monoxide as well. So, we're measuring all those four gases on a gas chromatograph.

Scott Bilby: For those field trials, are you getting enough biochar? Are you getting iit at the levels you require for the sort of tests you want to do?

Lukas Van Zwieten: We're very fortunate that we've got a good relationship with Best Energies in Gosford and I think we're getting the majority of the biochar that they're producing there for various clients. A problem at the moment is, what we need is very large amounts of biochar to do the large-scale field trials. At the moment we're limited to fairly small plots. That said, on the sugar cane plot up in the Tweed Valley we've got significantly larger plots there, but that was quite an effort in obtaining the amount of biochar required. Certainly in Australia there is no commercial source of biochar at the moment and that's why we're undertaking a range of scoping studies with Best Energy to take a look at the feasibility of getting pyrolysis units up and going.

Matthew Wright: Now, the produce of these farms - have you tried any of the sweet corn? What's the taste-test like?

Lukas Van Zwieten: It's absolutely magnificent! And I've given some of it to my friends and they're rapt with it as well. It's a really really nice corn. I don't know if my palate is quite up to telling the difference between the quality of the control plot and the plots where we have biochar on it but you can certainly notice a difference in the size of the cob and also the number of cobs. With the biochar treatment we've had more than double the number of cobs present than in the control plots.

Matthew Wright: So, is that cobs per stalk?

Lukas Van Zwieten: Effectively cobs per hectare.

Matthew Wright: Does that mean one stalk has more cobs on it?

Lukas Van Zwieten: That's correct, yes.

Matthew Wright: Are the stalk numbers the same.

Lukas Van Zwieten: The stalk numbers are about the same. However, in some of the control plots we've only been getting one salable-quality cob per stalk, whereas with some of the biochar treatments we are getting two very salable cobs per stalk, and there's certainly very big differences in the size of the cobs. And in some of the control plots, some of the corn didn't even produce a saleable cob either. So we are seeing some very different production qualities and quantities from these systems.

Matthew Wright: So, are you getting interest from sticky beak farmers looking over the fence wanting a piece of the action?

Lukas Van Zwieten: We've had a lot of interest, which I'm very happy to receive. But we've had a lot of questions and a lot of requests for biochar, and a lot of farmers wanting to do biochar trials on their farms. But unfortunately we don't have enough biochar to accommodate all these requests. However, as I've mentioned before once we get a commercial unit up and going; which is a very significant capital request, but is one of the few ways in which we can make a real difference to climate change and guarantee renewable energy and improve soil, then we'll have enough biochar that we can start doing some field trials on other commercial farms.

Scott Bilby: I'd just like to know whether Best Energies are likely to get some of commercial-scale pyrolysis plant up and running? I do recall you said that you're working together now to try and get something going.

Lukas Van Zwieten: We are current undertaking a scoping study for the North coast of NSW. That's in collaboration with Ballina Council and also with DSARD, another government department - Department of Sustainability and Regional Development. We're looking at a range of arrows I guess; the range of topics that need to align to make one of these units profitable and viable. We need to make sure that we have biomass resource. So, we need a minimum of 40,000 tonnes of biomass a year that's available to go into this pyrolysis unit. We need the biomass to be of low value, in other words biomass that would otherwise end up in landfill or that would be left lying around and generally no re-used in anything like gardens. We need to make sure that we get a reasonable price for the electricity we produce. We need to make sure that we have access to high-voltage power lines to put the energy back into. We also need a champion or a client that actually wants to do this. There are quite a lot of arrows that need to align to make the process viable, but I think that once the first unit is up and running in Australia, which will be the higher-risk unit because we're still testing the waters, I think then that it will be a snowball effect and a whole heap of industries, a whole heap of different sectors, will start seeing this as a serious technology for generating renewable energy, for waste minimisation, and also for producing biochar which is the area that I'm most passionate about, most interested in. We know that this biochar down the track will be suitable for carbon trading. We've got data with our collaborators in Forestry NSW showing that this biochar will last hundreds and thousands of years in the soil.

Scott Bilby: I'm afraid we've run out of time. That was fantastic.

Lukas Van Zwieten: That was too quick!

Listen to Podcast

ABC Catalyst: Agrichar - A solution to global warming?
Transcript

Tim Flannery 2007 Australian of the Year Talks about Char in an interview with 'Beyond Zero'

Johannes Lehmann - World's leading expert on Bio Char talks to 'Beyond Zero'

From the Journal Nature: Putting the carbon back: Black is the new green

From the Journal Nature: Biochar - A handful of Carbon

BBC Science: The Secret of El Dorado
Transcript