Biodegradable planter pots
Finding environmentally friendly, sustainable, and profitable uses for industrial waste products is an increasingly important issue for the business community both in New Zealand and overseas. This showcase focuses on the work done by Year 10 Kavanagh College Technology students Annabelle Weston, Charlotte Steele, Caitlin Spence, and Ike Saunders, who worked with Emerson's Brewery, Dunedin, to develop a bio-degradable planter pot using waste barley from the brewing process.
The project started with the "Grain Brains" team meeting their industry mentor Chris O'Leary from Emerson's, who explained the brewing process to give the team the right background for tackling the key issue of this project.
Chris explained that in the production of many beers, one of the most common by-products is barley husks or brewers spent grain (BSG), a difficult product to dispose of, especially for smaller inner-city breweries like Emerson's. A common solution is to sell the husks to farmers as cattle feed, but the team found that this was inefficient and unprofitable.
Breweries sell small amounts of grain to farms, but cattle need up to 10 kilos of grain per kilo of beef. Obviously this isn't profitable, so breweries are looking for more creative ways to rid themselves of BSG.
As Emerson's want to maintain strong green policies in everything they do, the negative effects on the company's carbon footprint when transporting the barley out of the inner city were another motivator for a new use for BSG.
The team had a brainstorming session on efficient, profitable, and ecological solutions to the problem, and came up with a diverse range of ideas for barley products, including fire-logs, breads, compost, and bird feed.
"Most of these possibilities used similar methods of recycling, it was just a matter of finding out which one was the most efficient," the team reported.
Eventually the team narrowed their ideas down to four solutions – muesli bars, bread, paper, and bio-degradable plant pots – and began researching their specific pros and cons.
It was here that the team came across the first big challenge that the BSG presented to them. From our first experiment on muesli bars we found that barley does not bond together well. Even after several additional tests trialling the recipe with bonding agents like honey and syrup we were left with a sticky, dry, unpleasant block.
The team had more success with a bread recipe, but, as barley wasn't a primary ingredient, it didn't use up enough BSG to be a viable option.
Paper making was the next idea the team trialled, using the Japanese method of nagashi-suki, an ancient yet effective technique that uses very few artificial chemicals and creates a high grade of paper. While the bonding issue was still a problem, the team managed to come up with a barley-to-water ratio that they felt was the best possible solution.
The final trial explored the option of biodegradable planter pots. The team used an existing product – peat planter pots – as their model to create a pot that would be bio-degradable within soil and could potentially have additional composites and nutrients added to the mix to help provide the plant with all it needs to grow.
Some research into the peat pots manufacture also provided the team with an added incentive for creating a planter pot from BSG.Peat pots aren't an environmentally-friendly product as the harvesting of peat destroys animal habitats and releases damaging amounts of carbon dioxide and methane into the atmosphere.
Realising that a viable BSG alternative to peat pots could reduce the demand for peat and have further environmental benefits, the team decided to make this their final product. However, the BSG's bonding issues were still a major concern, so the students experimented with gelatine and other adhesives, but all of them proved far too inefficient or costly to be a sustainable bonding agent. It was the team's previous research into a paper product that gave them their breakthrough – to use recycled newspapers as the bonding agent for the barley pots.
Newspapers could easily be sourced on a large scale from recycling stations in Dunedin. On a small scale, newspaper could be collected from the community to reduce strain on Dunedin's collection services and prevent double handling.
Convinced they had a winning idea, the team began a thorough testing process. Using purchased peat pots as a comparison and plastic seedling pots as a control, the team experimented with several different ratios of barley to newspaper, as well as mixing some with blood-and-bone fertiliser, to see which would give the best results in a controlled environment. Cress seeds were chosen for these trials as they are extremely quick to germinate.
During the trialling period the team also looked into the implications of using the same mix of paper and barley as weed matting, using the cress seeds as weeds in a series of experiments that have had very promising results so far.
The experiments were carried out in the controlled conditions of the school's greenhouse where observations on the seed's growth and the conditions of the pots were made daily during the regulated watering times. "We found that the barley planter pots were strong enough to support a plant in its first stages of growth and that when the plant no longer needs support the pot will degrade into the soil, providing further natural supplements."
Satisfied that the barley pots were an effective alternative to the peat varieties, the team looked into producing them on a larger scale, particularly how to speed up the two-day drying process. The team trialled cooking the pots, but found that, while drying time decreased significantly, the pots were sticking to the moulds. A small amount of cooking oil was applied to the moulds in a second trial, which helped the dried pots come out easily after being cooked and overcame the team's final hurdle.
"Our final solution has met the criteria of the challenge and exceeded our own expectations as we successfully developed a product that not only recycles barley husk but newspaper as well. The pot-making process is efficient and simple as both of the major ingredients can be sourced from local recycling stations and breweries. As our tests were only on a small scale there is also a lot of potential for further development."
The team's Technology teachers John Maguire, Chris Trewern, and Sue Robinson were impressed by what the team produced and by the practice they followed throughout the project.
The students worked diligently on their project outside of normal school activities and are dedicated, enthusiastic, and passionate about their achievement. This has been a challenging year for the team from Kavanagh College and teamwork was the key to the success of their outcome as they explored the significant variables that make a product successful.