Program ID: Innovation Anthology #204
Program Date: 02/19/2009
Program Category: Agriculture, Environment, Forests, Technology
Wheat Straw Pulp
PROGRAM #204 INTERVIEW WITH WADE CHUTE
MP3: 10.5 MB
Time: 11:30 Minutes
Wade Chute is the Team Teader for Pulp and Paper in the Forest Products Business Unit at the Alberta Research Council. His team has developed new technology for the production of wheat straw pulp.
CC: WADE YOU’VE BEEN WORKING FOR ALMOST TEN YEARS ON WHEAT STRAW. WHAT IS THE INTEREST IN WHEAT STRAW?
WC: That’s sort of a two part question. Part one is the ARC and its interest in wheat straw. There’s a tremendous source of fibre that’s available in the province of Alberta. And in a lot of cases there is surplus straw that’s available for commercial development.
This straw can make some pretty fantastic pulp, which we’ve seen here. And ultimately that pulp can be used in fairly high end papers, such as coated magazine paper as an example.
From the industry’s perspective, the opportunities that present themselves with wheat straw as a furnish are related to the green image, the greening of their image, an opportunity to include a little bit of wheat straw in their sheet gives them the perception of being environmentally sustainable and environmentally responsible.
CC: WELL WHY IS THAT?
WC: Well simply put, because wheat straw is an annually renewable by-product of food production. Everybody sees that crops grow here in the province of Alberta year after year after year. And they see the grain going into bread; they see the straw going into bales. And knowing that happens on a fairly short term gives the impression of sustainability.
CC: IS ANYBODY USING WHEAT STRAW RIGHT NOW IN THE WORLD?
WC: A lot of wheat straw is currently being pulped in areas where wood is of limited resource. Places like China and India as examples. Also, in places in eastern Europe such as Turkey. Wheat straw actually had a bit of a history here in North America as well being used to manufacture pulps for cardboard boxes and that was a development that was pretty much terminated in the 1940’s and 50’s.
CC: SO, WE WOULD CONSIDER RIGHT NOW THAT WHEAT STRAW MIGHT HAVE A LOWER QUALITY IMAGE. WHAT ARE YOU DOING TO CHANGE THAT?
WC: Well a lot of the problems that wheat straw has in terms of image is because the pulps that produced right now, especially in China, are produced for the Chinese market. The Chinese market demands are a little bit different than the North America market demands for brightness, for strength.
In China they will cook wheat straw to a higher yield, so they will remove less of the lignin. As a result they will bleach to a lower brightness. The lower brightness and the higher yield basically save them money, but it’s more than enough to achieve the paper objectives that they have there.
In North America, we seem to have this fascination with ultra high bright, ultra white, ultra pure printing and writing papers, and that necessitates that you cook to a much, much lower yield. It also implies that you use a lot more bleach.
So the straw pulp that’s produced in China right now, it’s not really inferior. They just cook it a little bit differently and they bleach it a little bit differently because of their own market needs.
CC: WHAT HAVE YOU BEEN DOING HERE AT THE ALBERTA RESEARCH COUNCIL TO IMPROVE THE TECHNOLOGY ON COOKING OR MAKING THAT WHEAT STRAW PULP?
WC: Well the approach that we’re taking here is trying to use wherever applicable relevant pulping technologies in a North American context. Chinese mills will typically use a soda pulping process, which is just sodium hydroxide. Here in North America we tend to use the kraft, pulping process which uses sodium sulfide in with the sodium hydroxide in order to cook wood fibre.
So using kraft pulping technology is something that we’ve also explored here on non-wood fibres, thinking more along the lines of how to adapt an existing pulping operation maybe with a small straw pulping operation right along side of it.
Other things that we’ve been trying to do to is address some of the industry’s concerns related to the technical performance of wheat straw within their own mills. There are two technical challenges that are associated with straw pulping. The first of which, and probably the largest of which, is silica.
Silica is basically a botanical component of the plant. Wheat straw will take up silica from the soil. It helps enhance its structure to keep it vertical as well as to impart a certain degree of rodent resistance.
Silica in a pulping feed stock will wind up reporting to the black liquor recovery loop and in the recovery furnaces tends to form glass which makes it very, very difficult to recover the cooking chemicals, which is a very important part of the economic viability of an existing pulp mill.
Top it all off with the reduction in heat transfer efficiencies, mills would be shutting down and chipping out their recovery boilers on a regular basis. And obviously that interrupts production. An interrupted production is loss in money.
The second technical issue that is quite common is…there are botanical components in wheat straw that inhibit drainage. Drainage basically refers to the rate at which water can drain from a fibre suspension.
The pulping process is a very wet process and you add a lot of water to a very little amount of fibre in order to wash it, in order to bleach it and stuff like that. Getting that water out of that pulp is very important. And if there’s a drainage issue with a specific feedstock, the problem is that washers tend to have to be much, much bigger in order to get a certain tonnage across it.
That causes an increase in capital cost and in some cases, an increase in operating cost. In all cases it affects the bottom line.
So ARC has been working on the development of technologies that will address silica and drainage. And to that end, we have actually patented a process that will remove silica from cereal straw prior to the chemical pulping process. This takes a lot of the burden off the chemical recovery loop and will ultimately enhance the performance of straw in a North American mill over what is current practice.
CC: NOW YOU HAVE A LITTLE PULP MILL OUT BACK. HOW DOES THAT WORK?
WC: Well what we have out the back here is a 10-tonne a day facility for processing cereal straw to remove the silica. The 10-tonne a day cereal straw desilication process winds up producing about 8.5-9 tonnes of straw where the silica has been effectively removed.
The problem is, we have a bottleneck after that part of the process and that bottleneck is in our chemical pulping capacity. We can desilicate 9 tonnes of straw in a day, but we can only cook five kilograms at a time.
To process 9 tonnes of straw at five kilograms per batch will take hundreds of years and that’s just beyond my lifespan.
CC: SO HOW DO YOU SCALE THAT UP SO THAT IT’S AT A LEVEL WHERE A LARGE MILL COULD ACTUALLY MAKE A BUSINESS OUT OF THIS?
WC: There is a bit of an infrastructure gap right now in being able to take the desilicated fibre and cook it such that it could wind-up being bleached and used in paper grades basically on a larger scale paper machine.
We have a 9-tonne a day product, 10-tonne a day in-feed desilication process but we can only cook five kilograms at a time. And again, it takes too long to generate the tonne quantities that are required by mills in order to evaluate certain paper grades.
Actually the Canadian Geographic release, their environment issue back in June of last year, that issue itself required 14 tonnes of wheat straw pulp.
Now 14 tonnes of wheat straw pulp would be derived from about 25-30 tonnes of desilicated wheat straw, 25-30 tonnes of desilicated wheat straw at five kilogram batches again is just, we lack the capacity to be able to cook on a larger basis.
CC: SO WHAT DO YOU NEED NOW TO GET THIS TECHNOLOGY TO MARKET?
WC: What we need is we need somebody to build a bigger one of what we’ve got is basically what it is. And while I can hope simply demonstrating the desilication process on a much larger scale than just cooking selected things in a five kilogram batch would be palatable to the industry. In a lot of cases they really need to see the cooking, they need to see the resulting black liquor; they need to see the bleached product going into a specific market at a certain price point in order for them to be able to justify a large capital expenditure.
In the case of wheat straw, and if we’re looking at building a satellite mill alongside an existing pulp mill, you know, just call it a non-wood pulping line, it’s a capital investment of up to and possibly even exceeding $200 million dollars.
$200 million dollars is a lot of money right now for the industry and there’s a lot of risk that’s associated with that obviously. So they need to answer some questions in terms of how it’s going to impact their existing process. They’re going to need to know that the markets are there for them at a certain price.
CC: SO IT SOUNDS LIKE A WORK IN PROGRESS?
WC: It is a work in progress. It’s interesting how much interest has been stimulated by the Canadian Geographic release. Within days of that magazine hitting the newsstands and the media that surrounded that event, we had telephone calls from very large reputable papermaking companies saying, ‘Well geez, where can we get some of this wheat straw pulp’.
Well, unfortunately right now, that answer would be in China. And unfortunately on a long term basis, I don’t foresee China being able to supply a large volume of wheat straw pulp for the North American market, largely because China is a net consumer of fibre. They bring in millions of tonnes of pulp every year to satisfy their own papermaking demands.
The opportunity to flow market pulp back from there to North America, I think, would be logistically challenging and once more, I don’t think it would be price competitive.
CC: ONCE YOU GET TO THE LEVEL THAT THIS CAN BE PRODUCED COMMERCIALLY, WHAT IS THE POTENTIAL MARKET?
WC: The properties of wheat straw pulp are very similar to hardwoods. In some cases they’re actually superior to hardwoods and in some cases they actually have slight setbacks against hardwoods.
Either way, there are certainly markets where wheat straw pulp can occupy a role. For example, wheat straw pulps are very good for imparting sheet smoothness. They are also capable of bulking out a sheet a little bit, so giving it a little bit more thickness for a given basis weight. And as such, the markets are really going to find themselves once commercial production comes on stream.
Unfortunately with the lack of commercial production, the uses of these fibres in the paper making context really can’t be explored.
Everybody who has had an opportunity to test a few kilograms on a lab scale, you know, ‘Ooh, this is kind of interesting or we can maybe try something along that line’. But really, what’s going to enable this industry to really take off and enable the market to take off, is to actually have a limited supply of wheat straw pulp out there for markets to really develop around.
A long time ago, hardwoods were produced as an inferior pulp. And they were produced because the fibre resource was essentially free. And what wound up happening was papermakers learned how to use these resources to the point where now hardwood is a common, as a matter of fact, probably a majority in most sheets of paper that are out there.
So, again, the same sort of story is going to happen with wheat. Get the pulp to the market, let the market figure out the way to use it best in terms of achieving their own needs, whether it’s sheet smoothness, whether it’s increased bulk, whether it’s increased tensile strength.
They’re going to find out how it’s going to be used. They’re going to add it in their own ways to make some pretty interesting papers.
CC: THANK YOU VERY MUCH WADE.
WC: It’s been a pleasure.