Alternative building materials (ABM) are defined as low-cost materials that “aim to reduce or eliminate the environmental impact of the construction” (Orhon and Altin, 2019, p. 728). ABMs can include materials that are energy efficient, resource efficient, reduce embodied energy, minimize greenhouse emissions, use rapidly renewable materials or have recycled content. The use of alternative building materials is mainly centered around plant-based fiber not obtained from trees and has the potential to become important in the future. While wood fiber is a renewable and sustainable material when harvesting and land conservation practices are performed correctly, the volume and need of fiber sources has the potential to tax our forest resources, leading to an increased focus on quicker rotation crops.

The Department of Sustainable Biomaterials at Virginia Tech focuses on preparing students for careers focused on the manufacturing, production, and use of forest products or other plant-based biomaterials. As a national leader in materials education, the department uses a variety of experiential learning (EL) methods for instruction. EL is a current trend in higher education pedagogy to promote active learning using real-world experiences (Kong, 2021). EL is largely based on Socratic practices and acts to pair knowledge with real-world situations including professional experience. Both authors have used EL methods in the development of project-based learning classes, where academic concepts are tied to real-world implementation scenarios. In 2017, the Department of Sustainable Biomaterials was awarded an exemplary department at Virginia Tech based upon the strength of EL pedagogy (Virginia Tech, 2018). Recent student interest has focused on various ABMs including hemp, bamboo, mycelium, and other natural materials. Current students show a high level of environmental literacy and are interested in entrepreneurial careers using non-conventional materials.

Kolb and Kolb (2005) noted that research efforts on EL have become interdisciplinary, which characterizes the student knowledge related to the Department of Sustainable Biomaterials, where students gain an appreciation of technical details, business knowledge and the use of sustainability assessment tools. EL theory characterizes for different learning approaches – diverging, assimilating, converging and accommodating – and further defines these areas as combinations of the four learning styles (experiencing, reflecting, conceptualizing, acting) (Kolb and Kolb, 2005). The EL experiences incorporated in the Department of Sustainable Biomaterials curriculum emphasize the use of reflection and conceptualization concepts to lead to action and experience, then complete the cyclic nature of this learning path by allowing more reflection, and re-conceptualization.

Hemp (Cannibis sativa) is one of the earliest cultivated crops, first used by humans approximately 8,500 years ago. Hemp has been used originally as a fiber source for cordage and canvas. Oils from hemp have also been used and are dominated by a current emphasis on cannabidiol (CBD). The story of hemp use is not complete without a mention of marijuana, an offshoot of hemp which contains high concentrations of tetrahydrocannabinol (THC), a psychoactive compound, that is currently regulated as a Schedule 1 drug (Malone and Gomez, 2019). Distinctions between hemp and marijuana are sometimes difficult and both plants have been banned from use. In recent years beginning with the Agriculture Improvement Act of 2018 (2018 Farm Bill), production of hemp in the United States was allowed. Current production has increased to where some states now allow growth of hemp with consistent monitoring to maintain THC levels less than 0.3 percent dry weight (Congressional Research Service, 2019).

Currently, most hemp production in the United States is being grown for oil production. However, there are optimal varieties available for fiber production, which is more common outside of the United States. Hemp fiber can be subdivided into two categories – bast, or outer fiber, and shiv (hurd) or inner fiber. The bast fibers are long, thin, continuous fibers with high tensile strength. Bast fibers are used in the production of clothing, insulation, and cordage. Hurd fibers are short, brittle and punky in nature, and are used in hempcrete production, as well as growth media, pulp and animal bedding (Fike, 2016).

Hemp-lime, formerly known as hempcrete, is a mixture of hemp hurd, lime plaster and water (Gołębiewski, 2018). The material is tamped into place and used as non-structural insulation material. The name was changed to hemp-lime since hempcrete sounds like concrete and may give the false impression that hemp-lime is a structural product. Insulation values of hemp-lime is R-2.08 per inch (Gibson, 2016), which is lower than conventional fiber-glass batts. Various manufacturers including Hempitecture, Inc.; Americhanvre; and American Lime Technology, among others, are available in the United States. Compared to other insulation types, hemp-lime has one of the lowest embodied carbon amounting to 0.142 kg CO₂eq./kg, compared to 1.35 kg CO₂eq./kg for fiberglass batt insulation (King, 2017). Therefore, even with a lower equivalent R-value of thermal resistance, hemp-lime can provide equivalent insulation with a reduced embodied carbon emission. An advantage of hemp-lime over conventional batt insulation materials is that hemp-lime can be extended beyond the stud wall cavity and be placed over top of the studs to prevent thermal bridging. Finishing materials for hemp-lime use a lathe and plaster system capable of withstanding local environmental conditions.

The disadvantages of hemp-lime are related to the installation of the material. Hemp-lime must be troweled into the wall section and restricted by forms to depths of 18 to 24 inches at a time before curing is complete, and the forms can be removed. This represents a significant amount of labor and time on the jobsite. Another disadvantage is the difference between working with bio-based fibers versus mineral aggregate. The hemp hurd itself will absorb a portion of the water used for the mix, so careful understanding of the mix is needed. Several companies (American Lime Technology, and others) sell pre-measured mixes which helps overcome this challenge, specifically on small scale projects.

The purpose of this article is to discuss previous teaching activities and suggest best practices for other educators to conduct such classes to help students gain the best experience in using hemp products, and other ABMs. When discussing novel construction materials such as hemp, there is often little information available as to the use and application of these projects. The use of EL methods can be helpful to engage students and allow for more creative exploration. EL was accomplished using a combination of classroom lectures, laboratory activities, and active engagement with industry professionals. The following sections include a description of the class, followed by perceptions of the students and faculty involved.

From the previous teaching listed above, the most impactful teaching methods appeared to be a combination of lecture-type instruction and project-based research. As the next iteration of EL related to hemp, Hindman and Hammett offered an independent study class called “SBIO 3984: Mycelium and Hemp” in the fall semester of 2023. As stated, “The purpose of the course was to explore the emerging uses of mycelium and hemp in construction. The class will consist of experiential learning to understand the sources, manufacturing, use and deconstruction of mycelium and hemp products in construction.” Students were evaluated based upon weekly homework assignments, and a final project, consisting of biweekly progress reports, and a final presentation.

One of the most persistent issues surrounding the use of hemp-lime is the perception that industrial hemp is cannabis. This issue was made clear to us early in our teaching when administration expressed concern about faculty possessing industrial hemp. Even among academics, there are many misperceptions and stereotypes related to the product. The issue is made murky by the fact that industrial hemp, which is defined as containing less than 0.3% THC, can produce elevated levels of THC during the growing process in response to environmental stressors such as extreme drought. This high THC level has led to destruction of crops and perceptions of higher risk associated with industrial hemp growing among farmers.

The authors felt strongly that the best approach to address concerns about industrial hemp vs. cannabis was to be honest and factual with our students. We openly discussed the differences between the two crops and highlighted the uses of industrial hemp and benefits to society. This view was shared by many of the guest speakers we invited, who mentioned that the legalization of industrial hemp growth has a tie to the cannabis industry. Making sure our students are prepared to describe their position and understand the issues of product legalization is important as they enter the workforce where they may face more opposition to industrial hemp use.

The topics and information shared in the class were very relevant to students and students approached the class very professionally, spending time and contributing deep work. Over a year after teaching this class, students still mention the course and its impact of exploration. Interest to repeat the class remains high. Topics such as hemp-lime, mycelium and more non-conventional biomaterials are of high interest due to their novelty. Whereas wood and traditional fiber sources have very dedicated and entrenched industries, more novel biomaterials are perceived as opportunities for entrepreneurial growth and a flatter corporate structure. This flatter corporate structure, which is more relaxed, appears more accessible to current students. There also seems to be a stigma that larger forest products companies often do more harm than good for the environment and do not represent significant efforts to improve the environment while creating products. Entrepreneurial opportunities and flatter corporate structure give students the hope that they can impact their corporate environmental footprint quickly and meaningfully.

While EL remains very popular in pedagogical circles, there is a significant time and energy commitment needed to create meaningful EL opportunities for students. There is a significant amount of preparation needed to create and lead students through these experiences versus traditional format classes. Experiential learning often requires more resources and time due to the reliance on specialized materials or substances. Open pedagogical activities such as a flipped classroom or student-directed learning require a greater range of preparedness, where faculty need to anticipate the direction of student thought, rather than steer students through a curriculum.

Student learning methods also have an impact upon EL activities. Many students in the Sustainable Biomaterials curriculum would describe themselves as tactile learners, so the use of EL manifests itself as more hands-on activities – students making hemp-lime in the laboratory, visiting local companies, interacting with professionals in meaningful ways. Obtaining materials and using lab space carry real costs that are often not accounted for in teaching allowance.

The use of project-based learning also has drawbacks as well. Often, the specific materials and test activities are not the main teaching element. Students also need to understand the importance of the process of conducting longer-term projects. From our experience, the most successful projects conducted in these classes include a large number of student milestones similar to Table 2. While the structure may seem excessive, the structure becomes most useful in the event of unexpected activities or challenges, where the project structure can help students re-orient themselves and adapt to new situations while maintaining the timeline.

The authors created the class “Mycelium and Hemp” with the intent that multiple materials would increase student learning about sustainable plant-based products in general. This was not an incorrect strategy, but in retrospect, the authors should have more carefully interrogated their own desires for the class.

As a faculty member is creating a class on novel materials, an important question to ask is the need for breadth versus depth of knowledge. Breadth of knowledge would be less technical-focused discussions and more comparative methods for different materials. Depth of knowledge would focus on more technical aspects and individual aspects of a single material. For the development of classes focused on novel materials, it is especially important to clearly elucidate educational goals.

Thinking more broadly about the spectrum of biomaterials available – wood, industrial hemp, bamboo, mycelium, straw, sheep’s wool, etc. – there are differences in these materials related to the current level of available knowledge and research. These materials could be placed on a continuum of different levels of knowledge. This continuum is offered to demonstrate the connection between relative material knowledge and the optimal pedagogical methods to transfer that knowledge.

The real success of this class was due to the response from guest speakers who were willing to lead tours or contribute their time to speaking with the students. Many of these speakers gave a current and realistic view of the industry, sometimes in less than perfect light, and were not afraid to discuss issues and inform students of challenges. This honesty is often hard to find, but is needed in the area of developing new products. The authors have encountered many students who have unrealistic visions of product use, which are often difficult to temper.

Visits to farm sites, processors and sales points are desirable but not always feasible. When travel was not possible, the use of Zoom facilities which allowed for audio and video communication were highly valuable, and able to place the guest speakers in the student’s space. The authors are immensely grateful for all of the guest speakers – in-person and virtual – who contributed to this class. Specific activities included:

The continued development of industrial hemp and other ABMs relies upon innovation and exposure of young building industry professionals to these products. Universities play an important role in inspiring and promoting the larger variety of available building materials throughout the industry. While Virginia Tech as an institution has several advantages such as agricultural researchers growing hemp, and the space available in the Department of Sustainable Biomaterials, there are opportunities to create similar experiential learning experiences that have been described here.

A distinct advantage of industrial hemp uses, and hemp-lime construction is that no specialized equipment is required for production. Given appropriate gloves, mixing can be performed with your hands if no other equipment is available. This contrasts with mycelium or similar materials, which require sterilization and higher cleanliness levels for processing.

Hemp-lime projects also have a very favorable scaling element. The sizes of samples constructed in Figure 1 were relatively small, while other universities and groups have conducted building-sized projects. The scalability makes hemp-lime very approachable and makes even small projects valuable in understanding the production method.

The authors also feel strongly that the success of courses related to industrial hemp or other ABMs should rely strongly on EL principles and theory. Typically, courses should begin with students reflecting on current literature sources and conversations with experts. Students can then begin to conceptualize their ideas of how to best use industrial hemp products and ABMs and then experience the use of materials through expert meetings and field trips. At this time, students can begin to craft projects which form the action portion of the learning activities. Finally, through the presentation of results and reporting, students reflect upon their experience and continue to refine their knowledge and views of industrial hemp and ABMs.