Due to its invasive nature, Japanese knotweed has been able to persistently grow across different terrains. According to data retrieved from the University of Georgia’s Center for Invasive Species and Ecosystem Health, Japanese knotweed has been detected in 43 out of 50 U.S. states6 . In addition to Japanese knotweed’s ability to grow across different topographies, it has been demonstrated to grow under harsh conditions which other plants might not. Specifically, a group of researchers conducting Japanese knotweed growth conditions studies describe how they expect the plant to continue growing and producing plant metabolites while placed in low-fertile soil with no irrigation. Currently, there exists numerous published techno-economic analysis studies of plantbased production focusing on biofuels , recombinant therapeutic proteins, industrial enzymes, and antimicrobial proteins for food safety. Here, this thesis will describe a process simulation model for the techno-economic analysis performed of the plant-based production of Japanese knotweed and for the extraction and purification of the biopolymer precursor, resveratrol, which has not been demonstrated before. This study establishes a framework to help inform decisions on the development of a domestic production route for such polymer precursors.Due to Japanese knotweed’s classification as an invasive species and predominant cultivation in China, literature focusing on optimizing its large-scale growth conditions and economics are limited. Luckily, grow bag gardening literature surrounding the production and harvesting of potatoes is vast. Potatoes are a subterranean root vegetables native to the Americas, making them a suitable candidate for modeling Japanese knotweed rhizomes after.

Thus, a techno-economic analysis for the upstream portion of the base case model was performed using data retrieved from UC DavisAgriculture and Resource Economics on potato harvesting. This model considered the different equipment needed, labor costs, land rent, the Capital Expenditure , and Operating Expenditures . The base case scenario assumes an annual production capacity of 100 MT resveratrol. To reach the proposed target, upstream production was modeled using an open-field, staggered plantation of Japanese knotweed plants of about 1,847 acres per batch. Each batch was assumed to have a duration of 2 years . Key assumptions for the proposed farmland in this chapter are listed in Table 2.1 A list of process assumptions used to define certain parameters within the model; FW, fresh weight, N/A, not applicable.In efforts to accurately model the upstream portion of resveratrol production, the cost of land rent for non-irrigated crop land in the U.S. was investigated. According to the USDA, the average rent paid for non-irrigated land in the U.S. is $128.00 per acre14. It determined that nonirrigated cropland for rent was available for $29.00 per acre in the southwest region of South Dakota15. Notably, the cost for non-irrigated land available in South Dakota was less than 77% of the national average. Due to the availability and affordability of farmland, South Dakota was chosen as the state best fit to model knotweed rhizome production in. Using research from the University of Georgia – Center for Invasive Species and Ecosystem Health, it was confirmed that Japanese knotweed can grow in west South Dakota . Next, South Dakota’s farm operations were assessed to determine whether the state would be able to handle the demand needed for resveratrol production. Using the mass of knotweed rhizomes grown per acre per the mass of knotweed rhizomes needed for 100 MT production of resveratrol, our estimates yield a total of 3,695 acres of non-irrigated land needed for suitable growth of Japanese knotweed needed to meet our target production level.

In 2021, the USDA reported South Dakota operating 43.2 million acres of land for harvesting ofcrops such as corn, wheat, soybeans, and sunflower16. Once the presence of Japanese knotweed in the state and available acres for farm operation was confirmed, South Dakota remained a suitable option for domestic production of Japanese knotweed.As mentioned above, certain assumptions were made during the design of the upstream production process model. The first assumption made was the concentration of free resveratrol present in Japanese knotweed rhizomes cultivated within North America. While the growth of Japanese knotweed in North America has been previously reported in scientific literature, the concentration of resveratrol and its glucoside, polydatin, are seen to differ between samples, ranging between two to three orders of magnitude. Further analysis demonstrated the impacts of seasonal variations, available nitrogen in the soil, and other environmental factors such as the presence of insects and fungus18 on the concentration of stilbenes present in Japanese knotweed plants. A variety of sources, shown in Table 2.1, describe an average free resveratrol concentration near 1.4 mg/g FW knotweed rhizome. When data on the total resveratrol, both polydatin and resveratrol, concentration were analyzed , the totalresveratrol concentrations in knotweed was determined to reach an average of 9.8 mg/g FW knotweed rhizome, 7-fold higher than for just free resveratrol. Using this information, the natural field grown Japanese knotweed rhizomes were assumed to contain free resveratrol and polydatin at a 1:3 ratio, specifically in concentrations of 0.5 mg/g FW and 1.5 mg/g FW, respectively. These concentrations and ratios fall towards the conservative range values but still align with the range present in Japanese knotweed.Another assumption made in the upstream process model was that there are no costs attributed to the biological containment of the knotweed within the field.

Notably, it is pertinent to mention here that knotweed has the ability of regenerating itself from small pieces of pre-existing rhizomes, as small as half an inch in length. Data provided by New Hampshire’s Department of Agriculture suggests it contains allelopathic properties causing it to release chemicals to eliminate native vegetation. Reports on Japanese knotweed growth have reported its ability to spread vertically for 10 ft and horizontally about 40 ft. Michigan’s Department of Natural Resources published an article mentioning knotweed rhizomes’ capability to penetrate depths of 7ft in certain soils . A bulletin written by researchers at Montana State University reported cases of Japanese knotweed creating monotypic stands while disrupting infrastructure like concrete in the process. No preventative measures were modeled although these may be necessary to fully contain the Japanese knotweed from spreading outward from the dedicated land for growing it. The model can instead be interpreted to have the fallow land surrounded by a deep and wide trench along its perimeter at minimum additional cost. As stated above, the practices required for upstream production of naturally grown Japanese knotweed followed potato harvesting practices listed by UC Davis Agriculture and Resource Economics Center. It is imperative to mention that the data provided on potato cultivation were grown in the intermountain region of California, along the Klamath Basin and not Southwest South Dakota as this model emphasizes. Nevertheless, the practices, equipment, labor costs, and investments are assumed to analogous for such production. The breakdown of the equipment, production practices, plastic grow bag and costs are described per practice in Table 2.4. First, the model assumed the acres of land needed for Japanese knotweed production had to undergo some preparation prior to planting. Here, 80% of the fresh acreage is assumed to be chopped using a heavy stubble disc and then any residual crops remaining after the initial cutting is mixed in with the soil using a ring roller. Once the mixing is complete, 50% of the acreage is assumed to undergo deep ripping in efforts to alleviate any harden soil. The first preharvesting procedure to be taken is the spread of a desiccant over some Japanese knotweed plants. The use of the desiccant is to prevent any further growing of the plant’s tops.

Notably, this step is a method used for potatoes and may not be suitable for Japanese knotweed production. While this step may not be required, it is applied in efforts to dry out the invasive Japanese knotweed found above ground. Here, the desiccant is only applied to 50% of the acreage using an aircraft. Once the desiccant has been added, the beds and vines of the Japanese knotweed plants are rolled and cut. The next step the model incorporates is the harvesting step. The Japanese knotweeds are dug up, harvested, and field cleaned in one step using a single tractor attached to a power take off driven four-row digger. The knotweed rhizomes which are harvested are then assumed to be placed in a 15-ton bottom-conveyor truck designated for transporting the rhizomes to a storage facility. Here, the truck is stationed and moved besides the harvester in the open-field to capture rhizomes as they are harvested. The transportation of the knotweed rhizomes is assumed to only be a 10-mile round trip from the field to storage facility. The transportation costs are shown below in Table 2.4. Once the trucks hauling the knotweed rhizomes arrive at the storage facility, the rhizomes are moved via a conveyor located on the back of the trucks onto a large holding tub where they are washed to remove any soil present. While downstream processing may only require the rhizomes stay in storage for a short time, storage fees were still included within our estimates. The total operational cost for the upstream portion was calculated to be slightly under $1.1 million dollars per year. A breakdown of the economics for each category is as follows. The labor rates used in the model were matched with the values used by the UC Davis Agriculture and Resource Economics Center. Specifically, the wage for a machine operator at $20.00 and $14.00 for general labor, including an overage charge of 37%. These values were understood to be the average industry rate as of January 2015 and were not updated for 2022 values. Within the model, the fuel, lube, and repair cost for each practice was estimated by multiplying the hourly operating cost for each piece of equipment for the selected practice by the hours per acres deemed necessary for potato harvesting. The hours needed per practice, cost of fuel , and repair cost used for this model was retrieved by the provided by UC Davis Agriculture and Resource Economics Center. The value used within their report is described as coming from calculations from the American Society of Agricultural Engineers and data from the Energy Information Administration, Department of Energy. The only material cost set when modeling the upstream portion was the cost of the desiccant. Cost for a desiccant for an acre of knotweed were aligned with the cost per acre to produce potato-chippers. Only two practices incorporated any custom costs, the pre- and post-harvest steps. The cost was attributed to the cost to operate the aircraft to spread desiccant and any cost which may be incurred when storing knotweed rhizomes.In addition to costs of each practice, a breakdown of the cash overhead was also shown in Table 2.4. Field sanitations described within the table refers to any sanitation services provided to laborers in the fields, such as portable bathrooms and hand washing areas. A single field supervisor is assumed to be managing the operations within the model. The wage was set to $57 per acre. Land rent values for unirrigated land in South Dakota were used as mentioned above. Liability insurance, the standard policy which is designated to help manage any expenses which may arise if an individual may sustain any bodily injuries while on the property, was set to $1 per acre. Notably, crop insurance is also an additional standard insurance provided to open-field growers which may provide coverage in the case of an unavoidable loss of crops. No crop insurance was estimated or used within the modeling of the upstream production of knotweed rhizomes. The next expense is attributed to any office expenses. Here, office expenses refer to any office supplies, telephones, road maintenance, booking and accounting and legal fees which may be incurred during production. The value was also aligned with the values listed by the UC Davis Agriculture and Resource Economics Center. Property insurance is an additional expense which was included in the cash overhead cost. Simply, property insurance accounts for any property loss and is charged at $1 per acre. The last expense is equipment investment repairs. Here, the repairs cost is associated with the annual preventative maintenance, set to $4 an acre. Once the cash overhead cost was calculated, the total annual operating cost or OPEX for the upstream production was estimated to be $1.4 million.