Agronomy and economics of two novel energy crops: Sida Hermaphrodita (L.) Rusby and Silphium Perfoilatum L.

The PhD project of title “Agronomy and Economics of two novel energy crops: Sida hermaphrodita (L.) Rusby and Silphium perfoliatum L.” was first conceptualised within the international project SidaTim. The main aim of the PhD was to reduce the uncertainty associated with the adoption of Sida hermaphrodita (L.) Rusby and Silphium perfoliatum L., through data gathering and evaluating their agronomic, economic and environmental performance. The main objectives of the PhD were: to review all available information and publications regarding the cultivation and energy production of the two species; to assess their agronomic performance in the UK; to examine the impact of their establishment on soil carbon; to determine their profitability against other potential crops across a European gradient; and to evaluate the greenhouse gas emissions associated with their cultivation. The novelty of the research lies on the establishment and assessment of two novel bioenergy crops in the UK compared across a range of climatic conditions, addressing the knowledge gaps regarding reliability and availability of information and assessment of their agronomic, economic and environmental performance. The first year of the project was dedicated to background research, collecting and processing the first set of soil analyses, producing all Silphium perfoliatum (L.) seedlings from seed, importing Sida hermaphrodita (L.) Rusby seeds from Germany, and in 2017 establishing an experimental site in Silsoe, Bedfordshire, UK. During the first three years,the mean maximum height of Sida hermaphrodita (L.) Rusby originated from seedlings was 198 cm and the maximum stem diameters were 14-18 mm. The mean maximum height of Silphium perfoliatum (L.) was 158 cm over three years and the maximum stem diameters were 14-16 mm. As opposed to the expected increase in maximum heights and diameters with time until plantation maturity, an overall reduction in maximum heights and diameters was recorded with time for Sida hermaphrodita (L.) Rusby, whilst only maximum diameters of Silphium perfoliatum (L.) decreased with time. Each year from February 2018, a winter harvest to measure the solid biomass production of Sida hermaphrodita (L.) Rusby and a summer harvest to measure the green biomass production of both Sida hermaphrodita (L.) Rusby and Silphium perfoliatum L. were carried out until September 2020. Mean dry biomass yields of Sida hermaphrodita (L.) Rusby plants grown from transplants for solid fuel for combustion were 1.7, 5.4, and 3.7 t DM ha⁻¹ in 2018, 2019, and 2020 respectively. Green biomass yields of Sida hermaphrodita (L.) Rusby for anaerobic digestion were on average 10.8, 8.1, 6.0 t DM ha⁻¹ in 2018, 2019, and 2020 respectively. The recorded declines in harvested biomass from Sida hermaphrodita (L.) Rusby are attributed to the combined effect of plant mortality, management and fertilisation practices. The corresponding mean green biomass yields of Silphium perfoliatum L. for anaerobic digestion were 4.6, 6.7, 8.9 t DM ha⁻¹ in 2018, 2019, and 2020. The second and third year focussed on objectives three and four, as well as collecting and processing the second set of soil analyses, data analysis, and writing up. The bulk density of the soil across 0-5 cm and 10-15 cm changed from 1.4-1.7 g cm³ prior to cultivation in 2017, to a uniform 1.4 g cm³ in 2020. The concentration of soil organic carbon at 0-5 cm decreased from 2.58% in 2017 to 1.85% in 2020, whereas at 10-15 cm, it increased from 1.86% to 2.12% over the three years. Overall, the mean soil organic carbon stocks (0-15 cm) declined from 65.0-67.6 t C ha⁻¹ in 2017 in 55.2-58.3 t C ha⁻¹ in 2020. The profitability of Sida hermaphrodita (L.) Rusby and Silphium perfoliatum (L.) was predicted over a rotation of 16 years and compared to that of an arable rotation and two other energy crops for the particular case of the UK and three other European countries. The calculated net present value (NPV) of Sida hermaphrodita (L.) Rusby was -1,591 £ ha⁻¹ without subsidies and 1,075 £ ha⁻¹ with subsidies; the corresponding net present values for Silphium perfoliatum (L.) were 3,031 £ ha⁻¹ and 5,607 £ ha⁻¹ . The study also calculated how much prices and costs would need to change for the NPV of the two crops to match the NPV of the most profitable energy crop or the arable rotation. Using an Excel model developed based on the IPCC guidelines, the greenhouse gas emissions for Sida hermaphrodita (L.) Rusby and Silphium perfoliatum (L.) production were calculated for a 16-year period. On a per annum basis, overall greenhouse gas emissions were estimated respectively at 4.2, 0.3, 2.2, -4.0 and -0.6 t CO2 eq ha⁻¹ for the arable rotation, short rotation coppice, Miscanthus, Sida hermaphrodita (L.) Rusby and Silphium perfoliatum (L.) systems. The environmental assessment demonstrated that cultivating Sida hermaphrodita (L.) Rusby and Silphium perfoliatum (L.) could potentially contribute to reducing greenhouse gas emissions.PhD in Water including Desig

On-farm greenhouse gas emissions associated with the cultivation of two new bioenergy crops in the UK

Before using novel energy crops to produce bioenergy, feasibility studies should be completed to determine their effect on net greenhouse gas emissions. The current study developed a model to study the greenhouse gas emissions associated with the cultivation of two novel bioenergy crops: Sida hermaphrodita (L.) Rusby and Silphium perfoliatum L., using Intergovernmental Panel on Climate Change (IPCC) guidelines. The establishment and cultivation of Sida hermaphrodita and Silphium perfoliatum were compared with an arable rotation, short rotation coppice (SRC) and Miscanthus. Under the assumptions specified in the current study, including annual fertilisation and a high root: shoot ratio for Sida, the cultivation of Sida hermaphrodita and Silphium perfoliatum resulted in a mean net emission of 3.0 Mg CO2eq ha−1y−1 and mean net sequestration of 0.6 Mg CO2eq ha−1y−1 respectively over a 16 year rotation. This compared to predicted mean net emissions of 4.2 Mg CO2eq ha−1y−1 for an arable rotation, and intermediate values for the SRC and Miscanthus crop (1.0 and 2.2 Mg CO2eq ha− 1y− 1, respectively)

Two novel energy crops: Sida hermaphrodita (L.) Rusby and Silphium perfoliatum L. - State of knowledge

Current global temperature increases resulting from human activity threaten many ecosystems and societies, and have led to international and national policy commitments that aim to reduce greenhouse gas emissions. Bioenergy crops provide one means of reducing greenhouse gas emissions from energy production and two novel crops that could be used for this purpose are Sida hermaphrodita (L.) Rusby and Silphium perfoliatum L. This research examined the existing scientific literature available on both crops through a systematic review. The data were collated according to the agronomy, uses, and environmental benefits of each crop. Possible challenges were associated with high initial planting costs, low yields in low rainfall areas, and for Sida hermaphrodita, vulnerability to Sclerotinia sclerotiorum. However, under appropriate environmental conditions, both crops were found to provide large yields over sustained periods of time with relatively low levels of management and could be used to produce large energy surpluses, either through direct combustion or biogas production. Other potential uses included fodder, fibre, and pharmaceutical uses. Environmental benefits included the potential for phytoremediation, and improvements to soil health, biodiversity, and pollination. The review also demonstrated that environmental benefits, such as pollination, soil health, and water quality benefits could be obtained from the use of Sida hermaphrodita and Silphium perfoliatum relative to existing bioenergy crops such as maize, whilst at the same time reducing the greenhouse gas emissions associated with energy production. Future research should examine the long-term implications of using Sida hermaphrodita and Silphium perfoliatum as well as improve knowledge on how to integrate them successfully within existing farming systems and supply chains

Comparative economics of Sida hermaphrodita (l.) Rusby and Silphium perfoliatum L. as bioenergy crops in Europe

The purpose of this research was to fill the identified gap on financial data of Sida hermaphrodita (L.) Rusby (Sida) and Silphium perfoliatum L. (Silphium), two perennial bioenergy crops that potentially provide a more sustainable alternative/complement to other bioenergy crops. Using discounted cash flow analysis, the Net Present Values of Sida and Silphium were compared to a rotation of other arable crops including maize, and the two energy crops of short rotation coppice and Miscanthus. The analysis was completed using the SidaTim analysis tool for the UK, Italy, Germany and Poland, producing a total of four independent models. The results showed that with no subsidies, cultivating Sida was unattractive in all four countries relative to other crop options. However, Silphium, was an economically viable option in each country. Both Sida and Silphium can offer greater environmental benefits than other arable crops, and the profitability of each crop would be further enhanced if additional payments for such public services were made to farmers, and if there were secure markets for the sale of the biomass. This study is the first comparative economic analysis in West and Central Europe of the two novel energy crops in comparison to more common energy crops and an arable rotation