Invasive Species as a potential resource
Invasive species are a major threat to the environment and the economy. In search of solutions to this issue, researchers have developed studies on how invasive species can be used in the civil construction sector, helping in the recovery of local biodiversity and minimizing the impacts arising from the production of construction materials.
According to the Great Britain Non-native Species Secretariat (GBNNSS), invasive species is any non-native animal or plant, which has arrived by human activity, either deliberately or accidentally and that has the ability to spread, affecting negatively the environment, the economy and public health . In most cases, they comprise plants that can create imbalances in local food webs and reduce overall biodiversity, through predation, competition or by transmitting disease. They can also intensify soil erosion, reduce groundwater recharge and diminish habitat for local wildlife.
The strategies to tackle them can vary. For invasive plants, for instance, there are three main methods of controlling: mechanical, chemical and biological. Mechanical control techniques usually refers to the mowing or mechanical cutting of an invasive plant infestation to limit seed production. It also includes constructing barriers to prevent an established invasive species from moving into a new area .
Chemical control involves the application of pesticides, herbicides, fungicides, or insecticides. Precautions need to be taken to limit the effects on surrounding non-target plants. Though effective, using chemical control can be unsustainable and very costly. As an example, the estimated cost to eradicate Japanese Knotweed with chemicals would be around £1.6 billion .
Biological control or ‘biocontrol’ uses a species’ own predators against them, like bacteria, fungi, viruses, or parasitic or predatory organisms, such as insects. However, the use of foreign organisms as a biological control must be carefully assessed, researched, tested, and monitored to ensure that the control does not become invasive itself. Although these techniques can be effective, they present risks and can be very expensive. Only in Great Britain, the control of invasive species costs the economy £1.8 billion per year .
The high costs and efforts of dealing with invasive species motivates designer to come up with diverse solutions to tackle them.
Although invasive species are a serious environmental problem, researchers are discovering their potential in the production of construction materials. This could relieve the pressure placed upon many of the native species used in the construction industry, benefiting both the natural and built environments. An example of this initiative is the project developed by the designer Brigitte Kock and the architect Irene Roca Moracia, and led by Professor Carole Collet. The project was part of the Maison/0 Sustainable Innovation graduate programme, a partnership between Central Saint Martins College in London and the LVMH group, a leader in luxury products, with the aim of developing a sustainable alternative to current building materials that could be used in luxury store interiors.
The team created a bioceramic tile utilising the by-products originated from the removal of two invasive species in the UK: Japanese knotweed and the American Signal Crayfish. These are among the non-native species that are causing the most ecological and economic damage in the UK. Signal crayfish are the main cause of the rapid decline in native crayfish through transmission of crayfish plague and Japanese knotweed undermines the structural integrity of buildings, in addition to outcompeting native plants .
For the development of the tiles, Brigitte and Irene were inspired by an ancient Romans recipe for concrete production. They adapted this ancestral recipe by replacing the volcanic ash used as binder in the Romans´ concrete by Japanese knotweed ash and root powder. For the aggregates, Irene and Brigitte used pulverized American Signal Crayfish shells instead of broken bricks and rocks that the Romans used . Combined with water and gelatine, these ingredients create a strong, homogenous material that cures and hardens without the need for added heat or synthetic coloring .
The final color and textures of the tiles depend on the curing times and the chemical reactions of the aggregates with the binder and water. Its colors range from a burgundy color, which is the result of the curing process when pieces of raw knotweed root are included along with the ashes, to a light green, created by burning the crayfish shell . The material can also assume different finishes, resembling raw concrete, marble or natural stones. According to Irene, this tiles could replace less sustainable and non-regenerative interiors materials, like concrete or limestone.
The use of invasive species in the production of construction materials has also been investigated by the students of the School of Architecture at Florida International University. They develop studies with Melaleuca Quinquenervia, also known as Melaleuca, a tree originally from Australia and New Guinea. Melaleuca became a major threat of the Florida Everglades ecosystem, as it is an extremely fast-growing tree. It reproduces at an alarming rate, being difficult to contain. It is also a very dense tree that displaces native plants and animals .
The Group studied the use of Melaleuca wood chips as aggregates for the production of a new type of a hybrid wood/concrete material, reducing the use of common aggregates in its composition.
For the development of the research, more than 30 customized mixtures were tested, using industry standard cylinders for compression tests. The students explored small variations in the amounts of Melaleuca wood chips, which not only produced different visual results in surface texture, but also differences in performance results. Furthermore, the inclusion of integral color dyes and textured formwork also provided a range of new material possibilities.
After the mixing tests, the students developed several prototypes. In partnership with a Florida state park interested in creating a butterfly garden, students developed full-scale mockups of seats, porous floors, planters and other architectural elements. According to the team, the material's ability to accommodate a variety of uses demonstrates its flexibility of use .
Studies have shown that the introduction of wood chip aggregate substitutes in the production of wood/concrete hybrid material presents several advantages in relation to traditional concrete. An example is the fact that the material is less dense , due to the presence of wood in its composition. It is also able to resist heat absorption throughout the day, offering the potential to reduce the Heat Island Effect in the urban environment .
The material is carbon negative, as the wood that makes up its core absorbs CO2 throughout its life. In addition, the use of Melaleuca tree wood chips can help relieve pressure from typical species used for building material. Moreover, by creating this new material, value is added to the by-products of invasive species, encouraging their removal efforts and facilitating the restoration of natural biodiversity.
Another example of architectural application for invasive species is the project Homegrown, proposed by Katie MacDonald and Kyle Schumann, founders of the studio After architecture.
The project is a temporary pavilion built at the South Garden of Tennessee’s Knoxville Museum of Art in 2020. The building was constructed entirely using panels made of fibers from kudzu and bamboo plants, invasive species in Tennessee. The panels take advantage of the natural mechanical performance and lightness of the plant´s fibers .
The fibrous waste materials were formed into the panels using a bio-based binding agent and a unique pneumatic forming system developed by After Architecture. According to Schuman, this system allows for the design and construction of an infinite number of forms through a malleable process — the injection and removal of air — which can be repeated several times. Using a reusable inflatable mold, the room’s walls were uniquely shaped for varying thicknesses and porosity. The resulting surfaces allows light to filter through the structure. From the outside, surfaces look flat, angular and solid. From the inside, the porosity of the panels is revealed along with their organic curves .
The studies presented demonstrate the great potential of the use of invasive species, transforming the threat that they present to the local environment into an opportunity for research and development of new construction materials. It shows that these species can not only be eradicated, but also valued. By creating architectural uses for invasive species, the construction industry can reduce the use of carbon-intensive materials, such as concrete, while developing mutually beneficial supply chains and protecting biodiversity. Furthermore, it can encourage the development of truly local solutions, as each region can develop specific strategies to combat its invasive species.
Author: Danielle Khoury Gregorio
Led by: Anna Juda
* Article originally published on the website bambouimmobilier.com
 House of Commons Environmental Audit Committee - Invasive species - First Report of Session 2019
 MORACIA, Irena Roca. LVMH climate week
 GELPI, Nick; ROVIRA, Roberto. Exotic Constructions: Incorporating Invasive Species in Design-Build Studio. Florida International University