Shives Research Articles

Exploring the Biomethane Potential of Different Industrial Hemp (Cannabis sativa L.) Biomass Residues

Industrial hemp stands out as a promising candidate for clean and sustainable biomass-to-bioenergy systems due to its multipurpose, high biomass yield and resource efficiency features. In this study, different hemp biomass residues (HBRs) were evaluated as a potential feedstock for renewable biomethane production through anaerobic digestion (AD). The biochemical methane potential (BMP) of the raw and pretreated fibers, stalks, hurds, leaves and inflorescences was investigated by means of batch anaerobic tests. The highest BMP was obtained with the raw fibers (i.e., 422 ± 20 mL CH4·g VS−1), while hemp hurds (unretted), making up more than half of the whole hemp plant dry weight, showed a lower BMP value of 239 ± 10 mL CH4·g VS−1. The alkali pretreatment of unretted hurds and mechanical grinding of retted hurds effectively enhanced the BMP of both substrates by 15.9%. The mix of leaves and inflorescences and inflorescences alone showed low BMP values (i.e., 118 ± 8 and 26 ± 5 mL CH4·g VS−1, respectively) and a prolonged inhibition of methanogenesis. The latter could be overcome through NaOH pretreatment in the mix of leaves and inflorescences (+28.5% methane production).

Anaerobic Co-Digestion of Cheese Whey and Industrial Hemp Residues Opens New Perspectives for the Valorization of Agri-Food Waste

Cheese whey (CW) and hemp hurds (HH) represent typically overabundant biowastes of food and agricultural production, and their circular management is crucial to improve both sustainability and profitability of the agri-food chain. By combining experimental biochemical methane potential (BMP) tests and literature data, the techno-economic aspects of a possible future bioenergy valorization of CW and HH through anaerobic digestion (AD) and co- digestion (coAD) were analyzed. Along the 42-days, BMP assays, CW, and HH alone rendered BMP values of 446 ± 66 and 242 ± 13 mL CH4·g VS−1, respectively. The application of coAD with CW and HH at a 70:30 ratio allowed to enhance the biomethane production by 10.7%, as compared to the corresponding calculated value. In terms of economic profitability, the valorization of HH as biomethane in a dual-purpose hemp cultivation could potentially enable net profits of up to 3929 €·ha−1, which could rise to 6124 €·ha−1 in case of coAD with CW. Finally, by projecting the biomethane potential from current and future available CW and HH residues in the national context of Italy, a total biomethane yield of up to 296 MNm3·y−1 could be attained, offering interesting perspectives for the sustainability of key sectors such as transportation.

Contribution to the Modelling of Coupled Heat and Mass Transfers on 3D Real Structure of Heterogeneous Building Materials: Application to Hemp Concrete

Bio-based materials, such as hemp concrete, have been widely recommended to reduce carbon emissions and energy consumption of buildings as a means of addressing current environmental problems. These materials may possess very interesting hygrothermal and acoustic performance. Hemp concrete is composed of hemp particles embedded in a binder that forms a very heterogeneous and porous component. The aim of this paper is to examine the influence of hemp concrete heterogeneity on the mechanisms of heat and mass transfer. The originality of this paper is to consider the real 3D structure of hemp concrete for modelling coupled heat and moisture transfers within the material. These 3D microstructures were obtained using 3D X-ray tomography reconstruction with a voxel size of 31.8 µm. Then, a specific finite element mesh was generated from the real, heterogeneous geometry of hemp shives, binder and interparticle air. A mesoscopic model was developed to simulate coupled heat and mass transfer phenomena within the material. The 3D temperature and relative humidity fields showed high heterogeneity and complex distributions that are governed by the hemp concrete morphology. In addition, the anisotropy of the material led to different effective thermal conductivities in each transfer direction. Numerical comparison with simulations performed on the fictive elementary representative volume of hemp concrete showed that consideration of the real geometry allows a better understanding of coupled heat and moisture transfer phenomena modelling.

Transparent Ultraviolet (UV)-Shielding Films Made from Waste Hemp Hurd and Polyvinyl Alcohol (PVA).

This work proposes a new approach to fabricate highly transparent and flexible composite films that exhibit enhanced UV-shielding properties. Lignin has innate UV-shielding properties. However, when purified lignin, which is conventionally extracted through chemical treatment, is mixed with polymeric materials, its presence negatively influences the transparency of the resulting composite. High transparency and UV-shielding are desirable properties for many applications. In this study, composites were made by mixing lignocellulose particles and polyvinyl alcohol (PVA), where lignocellulose particles were obtained from ball-milled waste hemp hurd without chemical treatments. The UV-shielding properties of the resulting composite film, as a function of hemp/PVA weight ratios, were investigated. The intermolecular interactions between the hemp particles and the PVA were characterized using infrared spectroscopy with the presence of –C=O group at 1655 cm−1, providing evidence that the chemical structure of lignin was preserved. The fabricated hemp/PVA films exhibit stronger UV-shielding, in the UVA-I range (340–400 nm) than TiO2/PVA films. The composite films also showed comparable water vapor permeability (WVP) with commercial packaging plastic film made of HDPE (high-density polyethylene). The optimization experiments were reported, with aim at understanding the balance between the UV-shielding and mechanical properties of the hemp/PVA films. The findings of this work can be applicable to the packaging, food and cosmetic industries where UV shielding is of utmost importance, hence adding value to hemp hurd waste.

Energy and carbon footprint assessment of production of hemp hurds for application in buildings

Construction is considered as one of the most relevant sectors in terms of environmental impacts, due to the significant use of raw materials, fossil energy consumption and the consequent Greenhouse Gases emissions. The use of unconventional and environmentally-friendly materials and technologies is worldwide recognised as a key factor to enable the decrease of material and energy consumption in buildings. Between natural/sustainable materials, those using hemp products and by-products (fibres and hurds) have rapidly widened their field of application in the building industry, mainly because of their good hygrothermal and acoustic insulation properties. Moreover, the usage of these materials allows high carbon storage due to the CO2 sequestration during the agricultural phase.This study represents an energy and environmental assessment of hemp crop cultivation in France, carried out through a Life Cycle Assessment approach, showing positive and negative contribution related to the different life cycle phases. The total CF evaluated through the IPCC, 2013 GWP 100 method (IPCC, 2013) is equal to 0.975 kgCO2eq, in view of a CO2 uptake of −1.29 kgCO2eq. So, it is understood that the total CF results therefore lower than the CO2 uptake due to the biogenic carbon captured and stored during hemp growth. The total Energy Footprint, instead, was calculated in 17.945 MJ. The Upstream phase came out as the main contributor to the impacts. A sensitivity analysis was performed to explore changes in results related to main inputs assumptions and, in particular, the environmental benefits associated with the replacement of conventional fertilisers (ammonium sulphate) with organic matter were highlighted.

On the theoretical carbon storage and carbon sequestration potential of hempcrete

Hempcrete is a natural insulation material that is well known for exhibiting favorable thermal properties and low manufacturing emissions. Hempcrete is a biocomposite, consisting of hemp shiv and a lime-based binder composed of hydrated lime and either a hydraulic (e.g., natural hydraulic lime and ordinary portland cement) or pozzolanic binder (e.g., metakaolin). While long-term biogenic carbon storage can be achieved via utilization of hemp shiv in hempcrete, additional carbon storage can be achieved via carbonation of the binder. This study advances previous carbonation modeling approaches by deriving a theoretical model based on the fundamentals of cement hydration and carbonation chemistry to quantify the total theoretical in situ CO2e sequestration potential of hempcrete binders. To estimate the percentage of manufacturing CO2e emissions that can be recovered through in situ binder carbonation, the model is implemented in life cycle assessments of 36 hempcrete formulations of various binder contents and densities using an equivalent functional unit (FU) of a 1 m2 wall assembly with a U-value of 0.27 W/(m2K). Our model estimates between 18.5% and 38.4% of initial carbon emissions associated with binder production can be sequestered through in situ carbonation. Considering biogenic carbon storage, we predict that the total life cycle CO2e emissions of hempcrete can be negative, with a minimum of −16.0 kg CO2e/FU for the hempcrete mixture formulations considered herein. However, we estimate that some hempcrete formulations can exhibit net-positive emissions, especially high-density mixes (>300 kg/m3) containing portland cement, thereby illustrating the importance of materials selection and proportioning in designing carbon-storing hempcrete.

Capillary Uptake Monitoring in Lime-Hemp-Perlite Composite Using the Time Domain Reflectometry Sensing Technique for Moisture Detection in Building Composites.

The use of waste plants in the production of building materials is consistent with the principles of sustainable development. One of the ideas involves using hemp shives as an aggregate for the production of a composite used as a filling of the timber frame construction of the walls. The most important disadvantage of using the building materials based on organic components is their susceptibility to the water influence. The wall material is exposed to rising groundwater. The research part of the paper presented the preparation method and the investigation of the hemp-perlite-lime composites. Flexural and compressive strength, apparent density, total porosity, thermal conductivity, and mass absorptivity were examined. The main research part pertained to the analysis of capillary uptake occurrence in the composites, being the important phenomenon present in the external walls. The study on this phenomenon was carried out using the technique of indirect moisture evaluation—Time Domain Reflectometry (TDR). The indirect readouts were additionally verified with the traditional evaluation using the gravimetric method based on the PN-EN 1925 standard. The study proved that the tested composites were characterized by low apparent density, thermal conductivity, strength parameters, high total porosity, and mass absorptivity. The partial replacement of hemp shives by expanded perlite had a beneficial effect on the tested properties of composites.

Electrochemical properties of nanoporous carbon materials obtained from raw materials of plant origin (hemp shives)

The paper reveals the results of electrochemical studies of activated nanoporous carbon material (NPC) as an electrode material for electrochemical capacitors (EC), the charge of which is accumulated in an electrical double layer (EDL). NPC material has been obtained from raw material of plant origin (hemp shives) by thermochemical activation using phosphoric acid. It has been established that there is an optimal ratio between the amount of acid and precursor based on plant biomass that is equal to 0.75:1. The specific surface area of ​​the obtained NPCwas ~ 2000 m2/g, and the maximum specific capacitance of EC models based on them was ~ 113 F/g. At the same time, the contribution of the EDL capacitance to the total capacitance is 60-80 %.

Experimental Investigations on the Performances of Composite Building Materials Based on Industrial Crops and Volcanic Rocks

Interdisciplinary and sustainability represent the main characteristics of this paper due to the fact that this research is offering a connection between two main areas—agronomy and construction, by using hemp shiv for the design of new building materials, which can increase the sustainability level of the building industry. For this reason, the main scope of this study is based on the investigation of a new category of composite building materials—lightweight mortars based on hemp shiv, volcanic rocks and white cement—which contribute to a positive environmental impact and help to increase indoor comfort. A complex report was carried out on two segments. The first one is focused upon the characteristics of the raw materials from the composition of the new materials, while the second segment presents a detailed analysis of these composites including morphological and chemical investigation, pyrolytic and fire behavior, compression and flexural strengths, and acoustic and thermal characteristics. The proposed recipes have as a variable volcanic rocks, while the hemp and the binder maintain their volumes and properties. The results were analyzed according to the influence of volcanic rocks on the new composites.

Physical properties of Australian hurd used as aggregate for hemp concrete

The purpose of this study is to determine the key properties of Australian hemp particles which are used for manufacturing hempcrete. Hemp characteristics have a wide variability due to the influence of the environment conditions in various farmed areas. This study focuses on the measurements of the mechanical, thermal and acoustic performances of three Australian hemp: unretted hemp hurd, retted hemp hurd, and hemp fines. Hemp hurd is usually used in non-load bearing building walls, and hemp fine, which is the by-product of hemp manufacturing industry, is usually incorporated into a render. The experimental results show that the main impact of the retting process is a decrease in bulk density and leading to an improvement in thermal and acoustic properties. Without compaction, the bulk density is ranged from 97 and 118.8 kg.m−3, the max sound absorption coefficient from 0.88 and 0.99, and the thermal conductivity from 64 to 97 mW.m-1. K-1. Hemp fines have excellent thermal and acoustic properties and appear to be an efficient aggregate to produce an insulating render. Australian hemps investigated in this study have shown very similar characteristics to European hemps.

Impact of hemp shiv extractives on hydration of Portland cement

When formulating materials containing an hydraulic binder and plant particles, the setting of the binder may be slowed or prevented by the compounds extracted from the plant. In this article, a methodology is fixed to analyse three types of hemp shiv and to study the variability of the composition of extractives and their influence on the hydration of cement. Isothermal calorimetric measurements have shown that one type of shiv caused a greater delay in the setting of the cement. Analysis of free compounds extracted from the plant has shown that this shiv has a higher content of extractives, and in particular, of sugar. By using the same quantities of standard sugars, it was found that the measured sugar content could not, in and of itself, account for the delay in hydration measured in the presence of shiv. Other extracted molecules, such as phenolic compounds, also play a part in the hydration of the cement.

Effect of compaction on multi-physical properties of hemp-black liquor composites

This study aims to develop fully agro-based insulating building materials. Previous studies investigated several types of aggregates and binders to develop composites. The thermal conductivity of such composite appears mainly impacted by the density. This paper aims to investigate the effect of density on various multi-physical properties of composites, using the same formulation and adjusting the forming step. Thus, specimens are produced with the same hemp shiv to black liquor ratio but different compaction stress. The effect of compaction on bulk density, porosity, mechanical resistance, thermal conductivity and Moisture Buffer Value (MBV) is analyzed. It is shown that it is possible to reach thermal conductivity that is low enough to be considered as building insulating material. Thanks to this study, the required compaction stress to ensure targeted values of density, then thermal conductivity and MBV, is identified.

Ecofriendly and innovative processing of hemp hurds fibers for tissue and towel paper

An innovative approach for preparing hemp fibers from hemp hurds for use in tissue and towel grades of paper is described. Hemp hurds are a low value by-product of industrial hemp processing that are generally used for animal bed litter. Tissue paper was fabricated from hemp hurd fibers by following three pulping processes: autohydrolysis (hydrothermal), sodium carbonate-based defibration, and high yield kraft pulping, and benchmarked against hardwood pulp. To meet industrial standards, hardwood and hemp pulp fibers were mixed at a dry mass ratio of 75:25, from which tissue paper sheets were prepared. Desirable tissue paper properties, such as water absorption, burst resistance, softness, and tensile strength (dry and wet), were measured and compared. Characterization of morphological and chemical properties of tissue handsheets was conducted with SEM and time-of-flight-secondary ion mass spectrometry (ToF-SIMS). The combined kraft pulped hardwood and autohydrolyzed hemp pulp fibers displayed improvements in tensile index, burst resistance, and softness of tissue handsheets compared to only kraft hardwood pulp handsheets without adversely impacting water absorption. Hardwood fibers showed a sparse distribution of surface lignin compared to hemp fibers using the same defibration. This technology can lead to a variety of eco-friendly tissue paper products that are not only highly energy efficient, but avoid harsh chemical processing.

Biosorbent from Industrial Hemp Hurds for Copper Ions Removal

Biosorbent from Industrial Hemp Hurds for Copper Ions Removal

A material proposed for re-use of hemp shives as a waste from fiber production

This work proposes a material obtained from hemp shives mixed with another industrial waste, clay from pottery, in a self-produced starch-based matrix. The preliminary results, obtained through Charpy impact, Shore D hardness and flexural tests, suggest that, despite both the ceramic and the ligneous fillers are effective to a point, the consolidation of the material needs improvement. This is confirmed by the significant presence of internal porosities, which coalesce during fracture. In particular, it would be necessary to reduce the dimension of hemp shives until obtaining a more regular fibrous geometry and applying a more uniform pressure on the whole section of the material.

Hemp-lime – contemporary usage of traditional materials

Hemp-lime is a comparatively unknown building material in Estonia. Scientific interest in this material is increasing remarkably quickly around the world, yet practical competence regarding its usage is lacking in Estonia, as far as construction is concerned.´
 Hemp occupies an important place amongst crops that have traditionally been cultivated in Estonia, but its use has not been typically associated with the construction industry. Owing to its strong fibre, hemp has primarily been seen as raw material for the production of textile products, particularly rope, and the inner core of the plant, or ‘hemp hurd’, has been cast aside as a by-product. Since the porosity of hemp hurds results in relatively low thermal conductivity, hemp lime, the composite material made by mixing hemp with lime, is suitable for insulating pre-existing building envelopes as well as for installing insulation for new buildings during construction. Lime creates an alkaline environment around hemp hurds, making it difficult for fungi and pest insects to thrive. Compared to other natural insulation materials, hemp-lime therefore has a rather good balance between durability and cost-effectiveness.
 The essential feature of hemp-lime relevant to construction engineering is that the material is monolithic – any occurrences of sparsity and the resultant risk of thermal bridging in building envelopes is kept to a minimum, since the hemp-lime filling that surrounds the load-bearing structure forms a solid external surface when properly installed. Owing to its high level of air-tightness, external structures made from hemp-lime can reduce the risk both of excessive cooling and of overheating. In addition to creating a comfortable indoor climate for residents, mitigating any sharp fluctuations protects the wooden construction elements surrounded by the hemp-lime, which also reduces the risk of moisture accumulation and frost damage.
 Reducing the annual energy consumption of buildings and ensuring healthy indoor air quality pose significant challenges to the construction industry, since according to the current building code, the energy performance indicator of buildings constructed from 1st January 2021 should not exceed the limit established for nearly zero-energy buildings. In short, this calls for more efficient use of resources, including the production, transport, installation, and recycling of materials. Compared to the majority of contemporary building materials, hemp-lime is relatively eco-friendly, and its energy content is low.
 Keywords: industrial hemp, lime, clay, hemp-lime, sustainable building materials

Properties of Aerated Hempcrete as a potential sustainable Building Material

Aerated concrete is lightweight concrete commercially available as aerocon blocks for the construction of infill walls. The compressive strength of these blocks varies from 4 to 6 MPa. This paper discusses the properties of aerated concrete by the use of mineral admixtures like fly ash, construction and demolition waste (C&D Waste) and hemp fibres. In order to reduce CO2 emissions, save energy and conserve natural resources, there is a need for reducing the production and consumption of concrete products. This paper manifests the investigations carried out to study the feasibility of using aerated Hemp concrete Blocks in Urban Housing. Industrial Hemp fibers have been identified to potentially absorb carbon. Hence the use of processed Hemp hurd can be used to develop concrete blocks. The aeration process and the complete elimination of coarse aggregates make the blocks light-weight and energy absorbing. In addition, the partial replacement of Cement with Fly Ash and sand with pulverized Construction and Demolition waste is also employed here, thereby providing a cost-efficient, energy-efficient and moreover, recyclable model. The properties of concrete containing these replacements were examined and it was concluded that this beneficial, high-silica content crop can be effectively utilized as a building material, without sacrificing the strength and performance of the concrete. Improvement in engineering properties of this aerated hemp block is also investigated in this paper.

Energy and moisture in historic masonry walls retrofitted with hemp-lime

Thermally insulating historic buildings is imperative in order to reduce energy demands of the existing building stock. Therefore an insulation material is needed that improves energy efficiency while being compatible with the existing structure from a hygrothermal, aesthetic and cultural heritage perspective. Hemp-lime is a building material that consists of on a combination of hemp shiv, the woody core part of the hemp stem, and building limes. The aim of this study was to determine if hemp-lime could be a feasible option for thermally insulating historic masonry walls in Sweden. The objectives were to measure energy performance of full-scale masonry façades insulated with hemp-lime and to monitor moisture levels inside the masonry walls. Three small single leaf masonry façades were constructed. One façade was uninsulated, the other had internal hemp-lime insulation and a third had external hemp-lime insulation. Energy use for space heating as well as temperature and relative humidity in the walls and rooms were monitored. Results show that thermally insulating historic masonry walls with hemp-lime can lead to an improvement in energy performance of 44-53 % compared to uninsulated single-leaf masonry. However, moisture levels were higher in the masonry façades that were insulated with hemp-lime.

Polylactide/hemp hurd biocomposites as sustainable 3D printing feedstock

Industrial hemp hurd (HH) is emerging as a bio-based filler in thermoplastic biocomposites. In this paper, HH/polylactide (PLA) biocomposites were developed as fused deposition modelling (FDM) feedstock through parametric analysis of the effects of HH loading with respect to melt flow, rheology, physical, thermo-mechanical, and mechanical properties of the biocomposites. Poly (butylene adipate-co-terephthalate) (PBAT) and ethylene-methyl acrylate-glycidyl methacrylate terpolymer (EGMA) were used as toughening and compatibilisation agents respectively in melt-compounding and extrusion to produce FDM filament. The FDM-printed standard samples were compared against corresponding injection-moulded biocomposites. The FDM filament exhibited a diameter tolerance within ±0.02 mm, and roundness variability below 0.03 mm, and the FDM-printed parts with HH loading under 30 phr showed higher impact toughness than the commercial PLA filament control. In addition, the FDM-printed samples exhibited greater dimensional accuracy with increasing HH loading.

Impact of Bio-Aggregates Properties on the Chemical Interactions with Mineral Binder, Application to Vegetal Concrete

Plant concretes were developed and are currently used as filling material in a timber frame. Their properties are strongly related to the bio-aggregates characteristics. In addition, since hemp shiv, the reference bio-based aggregate, has a limited availability, it is necessary to consider alternative bio-aggregates largely and locally available. Thus, this paper focused on identifying and understanding mechanisms of interaction between different bio-aggregates and mineral binders. To address this issue, the first objective was to determine the properties of five hemp shives and two alternative bioaggregates for vegetal lightweight concrete: corn and sunflower bark particles. The study of the chemical interactions between bio-aggregates and a pozzolanic binder was conducted on model pastes mixed with filtered solutions containing bio-aggregates extractives. The mechanical properties of the paste, as well as their hydration and their mineralogical evolution were studied. In the last part, the mechanical behavior of vegetal concretes was assessed. The results highlight a strong relation between the mechanical behavior of pastes and concretes and the extractive content of the different tested bio-aggregates. Finally, pastes appeared as a relatively good model to predict the behavior of concretes by following their early age performances: setting delay and 3-day mechanical strength.