Sustainable Straw Harvesting with Bill Pan

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Contact Bill Pan via email at

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Episode Transcription:

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Drew Lyon: Hello, and welcome to the WSU Wheat Beat Podcast. I’m your host, Drew Lyon, and I want to thank you for joining me as we explore the world of small grains production and research at Washington State University. We have weekly discussions with researchers from WSU and the USDA-ARS to provide you with insights into the latest research on wheat and barley production. If you enjoy the WSU Wheat Beat Podcast, do us a favor and subscribe on iTunes or your favorite podcasting app. And leave us a review while you’re there so others can find the show too.

[ Music ]

Drew Lyon: My guest today is Bill Pan. Bill is a Professor of Soil Science. He has worked in the Department of Crop and Soil Sciences for the past 34 years teaching soil fertility and plant nutrition courses and researching nutrient cycling and management, root development, and rhizosphere ecology. He has served as Department Chairman, Director of the Washington Oilseed Cropping Systems project, Director of the WSU partnership and the Regional Approaches to Climate Change USDA project, and now is co-leader with Dr. Tao of a NRCS Soil Health Project, while also serving as President-Elect of the Soil Science Society of America. Hello Bill.

Bill Pan: Hi Drew thanks for inviting me.

Drew Lyon: Thanks for being here and you are a busy man. [Bill chuckles] So I appreciate you taking the time to come and visit with me today. So as I drive around, I notice a lot more producers seem to be harvesting their straw. And I also know there’s a construction of a straw processing plant going on here in Eastern Washington. Can you kind of describe the history and current research activity related to that operation, the work that you’ve done in that area?

Bill Pan: Sure thing Drew. This is kind of a cool evolution of an idea that evolved in the mid ’90s and I did a sabbatical for University of Washington, got to know some folks in the Pulp and Paper Engineering Program, and Bill McKean, Mark Lewis over there at UW, myself, some students here and there starting getting together on a project to evaluate the feasibility of using wheat straw for cellulose fiber source to supplement the wood-based cellulose that goes into pulp and papermaking.

Drew Lyon: OK, so it’s actually possible for WSU and University of Washington to work together? That’s interesting. [both chuckle]

Bill Pan: Yeah, other than Apple Cup day it was truly a good Cougar/Husky collaboration.

Drew Lyon: So given the concerns about potential negative impacts of straw harvesting on soil and water quality, what are some of the basic principles of sustainable straw harvesting?

Bill Pan: OK, so we’ve started to develop a list of principles. And so I’ll go through them and we’ve got about seven of them. One is to think about precision straw harvesting and to try to focus your harvesting, if you decide to do this on, high residue fields that are producing a lot of straw obviously. So the idea would be not to remove straw from low productivity fields because you need to return all you can get in those fields to return the organic matter in the nutrients, as well as protect the soil surface from wind and water erosion. So pick the fields that are in highly producing areas and also possibly pick the fields or parts of the fields that are within your farm. You know, concentrate on the low-lying areas that produce more rather than the eroded hilltops for example.

Drew Lyon: Do you have kind of a threshold for what a high yielding, low yielding, which where you kind of draw the line at what you harvest and not harvest?

Bill Pan: Oh, gosh. That’s hard to tell but, you know, I would say try to avoid fields that are producing lower than 50 bushels per acre. You know, marginal is kind of 50 to 100 and then over 100 certainly you can afford to remove some of that straw.

Drew Lyon: Okay, good.

Bill Pan: The second thing is to make sure you leave some straw behind. So don’t cut it right to the ground but leave some standing there to meet soil conservation compliance. And then the third thing is rotate those fields that you’re harvesting straw from. So don’t go back to the same fields every year. Kind of spread it around to minimize the removal of the straw organic matter and nutrients. So spread around your farm and in the region. Make sure you try to direct seed back into those fields. So maintain those residues that you’re leaving behind on the soil surface to protect from wind and water erosion. The fifth thing is to make sure you replace nutrients in organic matters. So you are losing some of the carbon and plant nutrients by straw removal. You can do the math on nutrient removal verses additions from fertilizers over time. And so try to avoid mining your soil nutrients. And one way to do this is to think about the co-product that’s coming out of this plant, which is actually kind of once they extract the cellulose fiber they leave behind this co-product, which can be added back to the soil and it’s rich in carbon and nutrients that we’ll talk a little bit here. So the sixth things would be to try to monitor those harvested fields over time to make sure that you’re not drawing down nutrients and carbon too much when you’re harvesting the straw. And then the seventh one you actually alerted me to because you had been told or had noticed that along the road sides of some of the roads that where people had been transporting straw that weeds are starting to grow along these roadsides perhaps due to the weed seeds that get dropped from the straw bales. So try to avoid transporting weed infested straw. So those are the seventh principles.

Drew Lyon Okay, you mentioned leaving some straw behind, do you have some kind of rule of thumb? Is that six inches of stubble, three inches?

Bill Pan: Yeah, so NRCS actually goes by percent cover if you’re looking over the top of it. So they don’t really take too much into consideration, the standing straw, although I know that it really does slow down the wind speed so that’s why I like to be standing straw. But in terms of just soil surface coverage, they like you to maintain at least about 25% soil coverage. So if you were to look at a soil from overhead, you know, that 25% of that would be covered with straw.

Drew Lyon: Okay. So there’s a straw harvesting – before straw harvesting became something people did. People who thought they had too much residue used to burn fields. So could the straw harvesting maybe be a substitute for field burning, which has a number of negative connotations with it. Maybe straw harvesting might be a better way of reducing straw loads if you think you have too much?

Bill Pan: Yeah, actually that was one of the motivations that got me interested in this concept over the years was exactly that. And so we thought about this because there was quite a bit of field burning going on in the ’80s and ’90s. As people started adopting no-till and then they found out that, well heavy residue fields it was kind of hard to no-till your crop seed back into that field. And so there became a tradeoff burning your field first and then no-tilling, so it was kind of a trade — you could think of it as a trade of soil and water quality for a detrimental effect on air quality and maybe even health concerns. So that was kind of adventurous that attracted us and also the Department of Ecology got involved with funding some of our work. So there was — there has been quite a bit of research that’s been done by the USDA-ARS group here, looking at that tradeoff and they actually did replicated field plots. I know you were involved with that as well Drew. Burning the straw, removing the straw, leaving the straw, those kinds of options and looking at the effects on carbon and nutrient removal impacts on soil, that sort of thing. And so what they found was, and they did experiment two locations in Walla Walla and Pullman. This was Dave Huggins, yourself, Wayne Thompson was involved with WSU extension. And so the basic findings were that there was about 1.47 pounds of standing straw produced per pound of grain and that translates to, you know, for 100-bushel wheat crop or a 6,000 pounds of grain produced would produce about 9,000 pounds of standing wheat straw, dry wheat straw. And so what you guys found was that during field burn, a full burn would remove about 63% to 90% of that straw biomass would go up in the air and some of the ash minerals would fall to the ground. Where as baling removed about 65% of the standing straw leaving enough straw behind for conservation compliance. And the research has also documented nutrient losses to the system due to burning or baling and losses of essential nutrients like N, P, K, and S were valuated at fertilizer equivalence of about $52 and $42 per acre respectively for burning verses baling, not an insignificant removal of nutrient value by straw removal and that needs to be replaced if you want to avoid nutrient mining.

Drew Lyon: Okay and you mentioned earlier a byproduct of the straw plant being used to replace some of these nutrients and carbon. Are there other ways that the growers can replace or compensate for the losses of carbon and nutrients from straw harvesting?

Bill Pan: Yes, so there’s obviously you can replace it in the way of fertilizers and but, you know, when you think about it, using this co-product actually returns the exact ash minerals that you removed in the first place. So it’s this pulping process is a pretty simple process and it’s not what you would think about for a wood extraction, or wood pulping process that requires pretty harsh chemicals and some of that are kind of nasty to the environment. This is basically just using strong alkali and so you get that strong alkali plus the carbon that’s left behind in the lignin, hemicellulose is soluble sugars and the plant nutrients come back that are not volatilized. And so just to give you idea of the scale of this plant it’s going to be, running at full capacity, it’s going to be processing about 250,000 dry tons of straw per year. And so that means it’s going to be generating about 160,000 tons of this pulping co-product. And so and they’re going to recycle the pulping chemical about ten times so it actually concentrates the amount of stuff coming out of the non-cellulose stuff that’s coming out of the straw that’s left behind in the co-product. And once they get done with that ten times they’ll store it away in a vat and then they’ll concentrate it up to about 60%. So they’ll kind of evaporate it and make it more heavily concentrated so it’s easier to apply or it’s more concentrated for reducing transportation costs. So this bay rich in lignin and plant nutrients, and lignin is really what we think of in soil science is kind of the building block of soil organic matter. So if you were to pick one biochemical from straw that you definitely want to return it would be lignin.

Drew Lyon: Okay.

Bill Pan: And the cellulose that you use for making straw, making paper and cardboard, actually gets — when you put it in the soil it gets oxidized pretty fast by the microorganisms. It’s considered pretty good microbe food that they go after right away. So it goes up into the atmosphere as CO2 right away. Lignin is more stable, stays behind, builds that soil organic matter. So that’s a good thing to think about when you’re returning this stuff. So there’s ongoing research, there’s past research on the benefits of that, ongoing research by Dr. Tao and myself on thinking about ways to mix the co-product maybe with some lime to provide a unique liming soil amendment that might be able to move further in the soil. There’s some ongoing lab research on that right now. Other uses of this co-product are kind of interesting. They’ve already used it for road dust abatement, so spraying on roads to keep the dust down on gravel roads, rural road, and forest service roads. There’s actually an industrial lignin market for using it as a starting chemical for producing a number of things and then there’s this prospect for returning to the soil, which I believe needs to happen to really make this a sustainable system. So we did a bunch of research on this in the early 2000s and found that it did improve both, well all three of chemical, and biological, and physical properties of soils. So it’s pretty interesting stuff. And in itself, even without adding lime it is a mild liming agent since it uses strong alkali to pulp the straw in the first place.

Drew Lyon: And soil acidification is becoming quite an issue especially here in the Palouse.

Bill Pan: Right.

Drew Lyon: So that might be a benefit.

Bill Pan: Yeah, I think so.

Drew Lyon: Has there been any work done on — or will there be some work on if I remove eight tons of straw from my field, how much of this byproduct would I need to put on my field to replace the nutrients and the carbon I just took off?

Bill Pan: Oh yeah, no well, we haven’t developed any tables like that yet but that would be a good extension product I think [laughing], yeah, kind of a calculator.

Drew Lyon: Yeah, so you know, if I, as a producer know about how much I removed, this would tell me how much of this product would replace that.

Bill Pan: You bet and out of that project that I mentioned with you and Dave Huggins funded by Department of Ecology, there’s numbers in all of that data where we could generate a calculator like that.

Drew Lyon: Yeah, Okay. Neat. So if our listeners wanted to find out more about this work, is there a website they can go to or has some of it been published somewhere that they can go find or is that yet to happen?

Bill Pan: Yeah, well we have several research publications on various aspects of a system like that. It’s not housed in a good place so maybe we could put it up on your Grains Network site.

Drew Lyon: Okay, Small Grains?

Bill Pan: Yes.

Drew Lyon: Okay.

Bill Pan: And so yeah, we could easily do that.

Drew Lyon: Okay. Do you have any final comments about this rather exciting new area of work?

Bill Pan: Yeah, I think it’s really an exciting story for Eastern Washington agriculture. It’s really unique because this is actually the first pulp mill of any kind whether wood or straw that’s been built in the U.S. in over a decade. That’s kind of remarkable. And it’s also going to be one of the largest straw pulp mills in the world. So I believe if it’s successful it will serve as a model for more plants nationally and internationally. In terms of impacts in rural community, Columbia Pulp intends to hire about 25 to 30 people with their operation down there in little Starbuck, Washington. So I think that will be a great boom for the economy at Starbuck and Dayton. So just thinking in general if three tons per acre are harvested from productive fields to feed this plant it’s going to require about 83,000 acres per year to be harvested to provide that source of straw. So we obviously have enough acreage. We can move that harvested acreage around from year to year. They like to think in terms of maybe a 50-mile radius of the plant, keep it economical for transportation of the straw. And then we just recommend careful soil monitoring of the harvested fields just to make sure that, you know, you’re not doing any detriment to the soil quality. And then just, you know, we’re going to be working with the folks down there at the plant to do more ongoing field research. We’ll be working with the extension folks like Paul Carter down there to do some on farm trials of the application of the co-product.

Drew Lyon: It sounds like an exciting technology that can bring some profitability but we, like many things we have to be able to do it in a way that’s sustainable for both the company who is producing it and for the farmers in the fields who are participating in that activity.

Bill Pan: Absolutely. And you know, it’s one of these rare kind of value added products industries that’s coming to Eastern Washington, which we don’t have that many. And so I think it’s going to be good for the economy as well hopefully.

Drew Lyon: Okay, very good. Thanks for sharing some of your time with us. All right Bill.

Bill Pan: Thanks Drew for inviting me.

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Drew Lyon: Thanks for joining us and listening to the WSU Wheat Beat Podcast. If you like what you hear, you can subscribe on iTunes or your favorite podcasting app so you never miss an episode. And leave us a review while you’re there. If you have questions for us that you’d like to hear addressed on future episodes, please email me at You can find us online at You can also reach out on Facebook and Twitter @WSUSmallGrains. The WSU Wheat Beat Podcast is a production of CAHNRS communications in the College of Agricultural, Human, and Natural Resource Sciences at Washington State University. I’m Drew Lyon. We’ll see you next week.

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