Designing a Brick Alternative Using Mycelium and Agricultural Wastes

STEM I is taught by Dr. Crowthers. During STEM I, each student works on an individual research project. In the class, we learn how to brainstorm ideas, research and take notes, create a procedure, collect data, and analyze the results. At the end, all students create a poster and presentation to present their projects at February Fair.

Abstract

Kilns, which are used to produce ceramic bricks, release many harmful gases that negatively affect human health and can contribute to the production of greenhouse gases, but alternative building products have not been extensively investigated. Therefore, the goal of this project is to design a more eco-friendly alternative to bricks, using mycelium bio-composites and different agricultural wastes, that will help to reduce the harmful emissions of kilns and be a renewable, biodegradable material. Mycelium, the root fibers of fungi, will be grown into 3 variations of bricks with 3 different substrates in the same controlled environment. The material is grown, molded, and dried to create the final brick. After the bricks are complete, the grown bricks will be tested, along with a pre-grown competitor brick, for compressive strength and water absorption. Each test will have 3 trials and an average of the data will be used for comparison to a ceramic brick. The three substrates being tested are oak sawdust, rice bran, and hemp. The expected results are that rice bran, a substrate that is high in nutrition, should help the mycelium grow more and oak sawdust, a more durable and coarse substrate, could affect compressive strength and durability. Mycelium is an emerging bio-based material that still has a lot of unexplored potential in material science. By using different substrates, these tests will contribute to unexplored areas of research regarding the effects of different substrates on mycelium and determine the possibility of using mycelium in more eco-friendly building materials.

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Kilns, that are used to produce ceramic bricks, release many harmful gases that negatively affect human health and the environment.

The goal of this project is to design a more eco-friendly alternative to bricks, using mycelium bio-composites and different agricultural wastes, that will help to reduce the harmful emissions of kilns and be a renewable, biodegradable material.

Background Infographic

With climate change being a prevalent issue in society, there have been many initiatives to reduce greenhouse gas emissions. The construction industry is a big contributor to this pollution which is harmful for the environment. One of the main causes of these gas emissions in the industry are brick kilns (Khan et al., 2019). Bricks are an essential construction material used all around the world. In Asia alone, 1300 billions bricks are used every year. The main problem is the carbon footprint caused by brick production which releases 70.5-282.4 g of CO2 per kg of fired bricks (Prateep Na Talang et al., 2017). In addition to CO2, brick kilns also release waste products of SO2, CO, NOx, PM, and other fluoride compounds and carcinogenic dioxins. All these gases are the main causes of the depletion of the ozone layer and acid rain. These gases are also a main contributor to human health problems. Inhaling these gases causes many respiratory diseases such as lung cancer, chronic bronchitis, asthma, emphysema, cough sputum, wheezing, and dyspnea. Studies have shown that workers who are more exposed to brick kilns suffered more from these respiratory diseases (Khan et al., 2019).

Mycelium Background

With the large amounts of pollution caused by the construction industry, there has been a demand for to develop an eco-friendly building material that has low energy consumption, is sustainable, and functional. One emerging bio-based material is fungal mycelium. Mycelium is the root fibers of fungi that have the ability to obtain nutrients from waste substrates. The mycelium material binds together by growing into its lignocellulosic substrate (Maximino C. Ongpeng et al., 2020). The use of different substrates allows the material to grow on many agricultural wastes such as husks, waste fibers and residual stems. The material is fully natural and compostable. In addition, it has a wide variety of mechanical properties based on what fungal strain and substrate is used (Girometta et al., 2019).

Procedure

All mycelium material was purchased through Ecovative Design. 6 total bags of mycelium were grown, 2 for each substrate tested (hemp, oak sawdust, and rice bran). Each bag of material molded into 3 bricks. Gloves were used to handle the material and everything that touched the material (filter bag, gloves, measuring devices) was sprayed with 70% Isopropyl alcohol. To rehydrate the mycelium material, 4 tablespoons of flour and 3 cups of water was added. For the bags with oak sawdust and rice bran, 41 g of the additional substrate was also added to the bag. The bag was folded closed and shaken by hand to mix the materials in the filter bag. After, the bags were folded closed and sealed with binder clips. The bags were placed on a germination mat set to 78° C to regulate temperature. After 5 days of growing in the filter bags, the material was broken up by hand and 4 tablespoons of flour was added. After mixing the material with the flour, the material was pressed by hand into 3 brick shaped molds. The molds were covered with seran wrap and secured with binder clips. The molds were placed on the mat at 78° C to regulate temperature. After 5 days of growing in the mold, the bricks were placed on a baking sheet and baked in an oven at 200° F (93° C) for 4 hours. To test for compressive strength, the bricks were sent to a lab with a standardized testing machine for compressive strength. Each substrate mix, along with a competitor brick purchased from Ecovative Design, was tested in 3 iterations. To test for water absorption, the bricks were massed and the initial masses were recorded. Plastic boxes were filled with water and the bricks were left there for 24 hours. The bricks were taken out and massed again and the final masses were recorded in the spreadsheet. All data was analyzed using the ANOVA test and the Tukey test to determine if the differences in data were significant.

Figures

Mycelium Material Mycelium in Bag Mycelium Bricks Mycelium after being Molded

Results

A one-way between subjects ANOVA was conducted to compare the effect of different substrates on compressive strength in mycelium bricks. The compressive strength of the mycelium brick (*was significantly different/was not significantly different) with the use of different substrates based on the p-value of (*add p-value). *If significantly different, add: Post hoc comparisons using the Tukey test indicate that the mean for (*group 1) was significantly different than the mean for (*group 2).

A one-way between subjects ANOVA was conducted to compare the effect of different substrates on water absorption in mycelium bricks. The water absorption of the mycelium brick (*was significantly different/was not significantly different) with the use of different substrates based on the p-value of (*add p-value). *If significantly different, add: Post hoc comparisons using the Tukey test indicate that the mean for (*group 1) was significantly different than the mean for (*group 2).

Discussion/Conclusion

The objective, to design a brick alternative using mycelium, was supported by the results. The results show that (substrate) was the best substrate in making a brick among the three tested. Although the mycelium bricks were far from the standards of a ceramic brick, the results show the potential of continuing to change the material properties of mycelium.

(if hemp is the ideal substrate) The results agree with existing experiments that show that hemp is the most ideal substrate in construction due to its low water absorption. In the experiment, the researchers hypothesized that this was due to the high density of mycelium with hemp (Elsacker et al., 2019). This is (supported/refuted) as mycelium with hemp (had/didn’t have) the highest density among the 3 substrates. Additionally, that experiment found that all the tested mycelium bio-composites had water absorption coefficients less than a standard brick and that these results were 180%-350% lower than other studies (Elsacker et al., 2019). This is (supported/refuted) as the water absorption coefficients were (higher/equal) to the ones in the study. In a literature review of mycelium, it was found that compressive strength for bio-composites ranged from 27-567 kPa (Girometta et al., 2019). This is (supported/refuted) as (all/some/none) of the data for compressive strength were within this range.

The findings in this paper contribute to the continued research into the potential material properties and applications of mycelium bio-composites. The paper establishes a methodology to successfully grow mycelium bricks at home. The results show that there is a significant impact that the substrate has on the durability and water absorption of mycelium. Further work is required to fully develop a mycelium brick alternative that meets the standards of a ceramic brick.

References

Elsacker, E., Vandelook, S., Brancart, J., Peeters, E., & Laet, L. D. (2019). Mechanical, physical and chemical characterisation of mycelium-based composites with different types of lignocellulosic substrates. PLOS ONE, 14(7), e0213954. https://doi.org/10.1371/journal.pone.0213954

Girometta, C., Picco, A. M., Baiguera, R. M., Dondi, D., Babbini, S., Cartabia, M., Pellegrini, M., & Savino, E. (2019). Physico-Mechanical and Thermodynamic Properties of Mycelium-Based Biocomposites: A Review. Sustainability, 11(1), 281. https://doi.org/10.3390/su11010281

Khan, M. W., Ali, Y., De Felice, F., Salman, A., & Petrillo, A. (2019). Impact of brick kilns industry on environment and human health in Pakistan. Science of The Total Environment, 678, 383–389. https://doi.org/10.1016/j.scitotenv.2019.04.369

Maximino C. Ongpeng, J., Inciong, E., Sendo, V., Soliman, C., & Siggaoat, A. (2020). Using Waste in Producing Bio-Composite Mycelium Bricks. Applied Sciences, 10(15), 5303. https://doi.org/10.3390/app10155303

Prateep Na Talang, R., Pizzol, M., & Sirivithayapakorn, S. (2017). Comparative life cycle assessment of fired brick production in Thailand. The International Journal of Life Cycle Assessment, 22(11), 1875–1891. https://doi.org/10.1007/s11367-016-1197-3

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