Shielding Effectiveness Measurements of Drywall Panel Coated with Biochar Layers

Shielding against electromagnetic interference (EMI) is a critical issue in civil applications generally solved with metal screens. In recent years, the properties of many composite materials filled with carbon nanotubes or graphene or materials with a carbon-based coating have been analysed with the aim of using them for electromagnetic shielding applications. Among other carbon materials, biochar, derived from biomass and characterized by high carbon content, emerges as a sustainable, renewable, environmentally friendly, and inexpensive material. In this paper, commercial biochar thermally treated at 750 °C is used to coat with several layers common building components such as drywall panel. Shielding effectiveness is measured in the frequency band 1–18 GHz for normal incidence and skew angles 10, 20 and 30 deg in a full anechoic chamber with double ridged, vertically and horizontally polarized broadband horn antennas. The results show that the proposed biochar-coated drywall panels provide a good shielding effectiveness compared to similar solutions, with the advantage of a less expensive and easier to realize building material

Low cost maize stover biochar as an alternative to inorganic fertilizer for improvement of soil chemical properties, growth and yield of tomatoes on degraded soil of Northern Uganda

Background Soil fertility decline due to nutrient mining coupled with low inorganic fertilizer usage is a major cause of low crop yields across sub-Saharan Africa. Recently, biochar potential to improve soil fertility has gained signifcant attention but there are limited studies on the use of biochar as an alternative to inorganic fertilizers. In this study, we determined the efect of maize stover biochar without inorganic fertilizers on soil chemical properties, growth and yield of tomatoes (Solanum lycopersicum L.). A feld experiment was conducted in 2022 for two consecutive seasons in Northern Uganda. The experiment included fve treatments; inorganic fertilizer (control), biochar applied at rates of 3.5, 6.9, 13.8 and 27.6 t ha−1. Results In this study, maize stover biochar improved all the soil chemical properties. Compared to the control, pH signifcantly increased by 27% in the 27.6 t ha−1 while total N increased by 35.6% in the 13.8 t ha−1. Although P was signifcantly low in the 3.5 t ha−1, 6.9 t ha−1 and 13.8 t ha−1, it increased by 3.9% in the 27.6 t ha−1. Exchangeable K was signifcantly increased by 42.7% and 56.7% in the 13.8 t ha−1 and 27.6 t ha−1 respectively. Exchangeable Ca and Mg were also higher in the biochar treatment than the control. Results also showed that plant height, shoot weight, and all yield parameters were signifcantly higher in the inorganic fertilizer treatment than in the 3.5, 6.9, and 13.8 t ha−1 treatments. Interestingly, maize stover biochar at 27. 6 t ha−1 increased fruit yield by 16.1% compared to the control suggesting it could be used as an alternative to inorganic fertilizer. Conclusions Maize stover biochar applied at 27.6 t ha−1 improved soil chemical properties especially pH, N, P and K promoting growth and yield of tomatoes. Therefore, maize stover biochar could be recommended as an alternative to expensive inorganic fertilizers for tomato production in Northern Uganda

Biochar production and characterisation - a field study

Biochar is a solid residue produced from pyrolysis, which is the heating of biomass in the absence (or near absence) of oxygen. The use of biochar can potentially aid in mitigating climate change through carbon sequestration and improve soil quality by the addition of nutrients, increased water holding capacity and providing a liming effect in soils. The physical and chemical properties of biochars can vary depending on pyrolysis conditions and feedstocks used. The majority of research to date focuses on biochar production in laboratory conditions or from commercial reactors and there is less research on biochar production using appropriate technology for resourceconstrained communities. The current work details preliminary results of the characterisation of biochars produced using an earth pit and a prototype top-lit up-draft (TLUD) stove. Analyses were conducted for yield, elemental composition, pH and water uptake of the biochar. Five types of feedstocks were used – pea straw, single-source woodchips, multi-source woodchips, sticks and branches, and leaves and twigs. The results indicate that as expected feedstock impacts both quality and quantity of biochar produced, and different production methods may be more suitable for different feedstock. The earth pit produces a larger yield than the TLUD stove for pea straw and fallen biomass (12 v/v% for pea straw, 6 v/v% for leaves and twigs, and 25 v/v% for sticks and branches compared with 2 v/v% for each, respectively). However, the TLUD stove produces higher quantities of biochar for single-source wood chips (34 v/v% from the TLUD stove vs 10 v/v% from the earth pit). The difference in elemental composition for biochar from different feedstock material is significant, however, the production method has little impact, indicating that the degree of devolatilisation from each method is similar for each feedstock. The pH of all biochars is high and in the range of 9.3-10, which may be attributed to their high ash content. In addition, pea straw biochar has a greater water uptake compared with biochar from the other wood-based feedstocks, as expected. In a humanitarian context, the results indicate that both production methods are suitable for producing a highly alkaline biochar with a similar water uptake capability. The high alkalinity of all biochars shows that acidic soils could potentially be improved by the biochar produced from either system. Drought-susceptible soils can potentially be improved to a slightly greater degree with addition of pea straw biochar.Mathu Indren, Nishanth Cheruvu, Cristian Birzer and Paul Medwe