Agricultural Biomass Residues Research Articles

Particle size-dependent anti-corrosion and mechanical behavior of green-graphene composite

In this study, Green graphene (GG) was synthesized from residual agricultural biomass through pyrolysis and prepared various sizes (2D, 37 μm, 45 μm, 53 μm, and 100 μm) via mechanical and liquid phase exfoliation. These GG samples were incorporated into an EP matrix, forming GG/EP composite coatings for carbon steel. Corrosion resistance was assessed via PDP and EIS techniques. The 37 μm-GG/EP composite coating also showed uniform distribution and compact surfaces. The 37 μm-GG/EP composite coating displayed higher corrosion inhibition (99 %) owing to the even distribution of GG within the EP matrix than the uncoated, along with enhanced hydrophobicity, tensile strength (61.3 %), fracture strain (77.2 %), and toughness (90.5 %) than pure EP coating. Improved corrosion resistance, which was found related to three main factors: first, GGs enhance the coating integrity by obstructing pores and flaws, to stop corrosive media from penetrating. Second, the well-dispersed GG sheet lengthens the diffusion pathways for corrosive agents to the carbon steel substrate, consequently lenghtening the corrosion process. Third, at 37 μm size the resititve forcefields of the GG/EP structure become the most effecitve agaisnt the corrosive media. The study also establishes GG as an eco-friendly sustainable alternative of non-renewable resource based mined compounds of Zn, etc. that are universally and traditionally used, for protective coatings.

Techno-economics and environmental sustainability of agricultural biomass-based energy potential

This paper explores the viability of utilizing agricultural biomass-based energy potential, employing mathematical, engineering, and economic modeling techniques. Moreover, the potential of a biogas-based co-digestion (CD) system, integrating its techno-economic performance and environmental sustainability in terms of electricity generation, has also been studied. In this investigation, the categorization of 25 different plant species into two groups: arable field crops (AFCs) and horticultural plants (HPs), was performed. Data was collected during the 2021‐–2022 cropping season in Bangladesh from various sources, including literature reviews, governmental, and non-governmental organizations. The findings revealed that the available agricultural biomass residues, totaling 1,02,585.75 KT, have the capacity to generate 1,33,815 million m3/year of biogas. This energy potential corresponds to 291,125.85 TJ/year or 9231.60 MW of electricity, which can fulfill 88% of the national total energy demand. In terms of levelized cost, the proposed approach is more competitive and shows a greater promise compared to other technologies. Furthermore, it demonstrates environmental friendliness by reducing CO2 emissions by 156 tons at a cost of $7/ton while earning $1092 annually from the potential carbon-credit market. This approach presents a potential solution to address Bangladesh's energy crisis. The payback period of the system ranged from 2.93 to 3.75 years, with and without the inclusion of a slurry, respectively. The recommended methods hold significant promise for meeting national energy demands. A case study was provided as a proof-of-concept (PoC) to validate the approach. This study is the first of its kind, providing valuable insights into the renewable energy potential in Bangladesh. The results will assist policymakers in formulating sustainable energy policies.

Application of persulfate-assisted graphitic carbon, derived through pyrolysis of waste biomass, driven by visible light, for the removal of tetracycline from water: Mechanisms and performance influencing parameters

Sulfate radical based advanced oxidation process by using carbon-based materials has attracted widespread attention for removal of emerging contaminants in water. This paper reports the study on the efficacy of visible light activated persulfate (PS) – graphitic carbon (GC) system for the removal of tetracycline (TC) from water . Here GCs from residual agricultural biomass were synthesized via a facile and chemical-free pyrolysis route, and their characteristics were analyzed under varying thermal conditions, viz. temperature (550–950 °C) and heating rate (2.5–10 °C min−1). The GCs at high pyrolysis temperatures (> 700 °C) revealed graphitic and condensed aromatic carbon networks with enhanced textural properties, facilitating electron-mediated reactions through interconnected morphology. The methodology is derived from the research that shows certain pyrolysis derived carbon products are known to have transient photocurrent response, indicating semiconductor properties. Here, the visible light-driven GC/PS (950 °C, 5 °C min−1) system resulted in high TC removal efficiency of 91.23% within 180 min compared to other PS/GCs prepred under different conditions. The mass spectroscopy data shows that the GC/PS system successfully degraded TC into simpler products and achieved the highest mineralization efficiency of about 65.43 ± 3.62%. The radical scavenging experiments revealed that 1O2 and •OH were the dominant reactive oxygen species suppressing degradation of TC by 13% and 9%, respectively. It can be surmised that both radical and non-radical pathways facilitate TC degradation via dehydration, demethylation and oxidation of aromatic rings- due to both catalytic and physico-chemical properties of GC/PS .

Optimized Extraction of Glycosylated Flavonoids from Pepper (Capsicum annuum L.) Agricultural Biomass Residues through Ultrasonic Pulse-Assisted Natural Deep Eutectic Solvents

Optimized Extraction of Glycosylated Flavonoids from Pepper (<i>Capsicum annuum</i> L.) Agricultural Biomass Residues through Ultrasonic Pulse-Assisted Natural Deep Eutectic Solvents

Immobilizing white-rot fungi laccase: Towardbio-derived supports as a circular economy approach in organochlorine removal.

Despite their high persistence in the environment, organochlorines (OC) are widely used in the pharmaceutical industry, in plastics, and in the manufacture of pesticides, among other applications. These compounds and the byproducts of their decomposition deserve attention and efficient proposals for their treatment. Among sustainable alternatives, the use of ligninolytic enzymes (LEs) from fungi stands out, as these molecules can catalyze the transformation of a wide range of pollutants. Among LEs, laccases (Lac) are known for their efficiency as biocatalysts in the conversion of organic pollutants. Their application in biotechnological processes is possible, but the enzymes are often unstable and difficult to recover after use, driving up costs. Immobilization of enzymes on a matrix (support or solid carrier) allows recovery and stabilization of this catalytic capacity. Agricultural residual biomass is a passive environmental asset. Although underestimated and still treated as an undesirable component, residual biomass can be used as a low-cost adsorbent and as a support for the immobilization of enzymes. In this review, the adsorption capacity and immobilization of fungal Lacon supports made from residual biomass, including compounds such as biochar, for the removal of OC compounds are analyzed and compared with the use of synthetic supports. A qualitative and quantitative comparison of the reported results was made. In this context, the use of peanut shells is highlighted in view of the increasing peanut production worldwide. The linkage of methods with circular economy approaches that can be applied in practice is discussed.

Moisture content effects on self-heating in stored biomass: An experimental study

Biomass is essential for modern bioenergy applications, but long-term storage of large volumes of it can pose challenges to plant safety due to the intrinsic self-heating characteristics of biomass piles. In recent years, serious fire accidents have occurred because of self-heating. However, little research has been conducted on this concern. The effects of different initial moisture contents (range of 20–95 %) on the self-heating characteristics of rice and wheat straw, which are two different agricultural biomass residues, are investigated in this study. Biomass samples with different initial moisture contents are stored in a well-insulated container, and the temperature and oxygen levels within the stored biomass samples are monitored. Based on the tests, the heat production rate, oxygen consumption rate and microorganism growth rate are derived, and the impacts of the initial moisture contents on the self-heating characteristics of the stored biomass samples are analysed. The highest temperatures in the stored rice straw and wheat straw are attained under initial moisture contents of 50 % and 20 %, respectively, while the largest heat production rates for both straw types are attained under an initial moisture content of 95 %. An increase in the initial moisture content greatly enhances the overall biological reactivity and oxygen consumption rate. The heat production and oxygen consumption levels exhibit a clear positive correlation. Under identical storage conditions, wheat straw is more susceptible to self-heating than rice straw, as shown by its higher heat generation, faster oxygen consumption, and shorter temperature peaking time. This study contributes to a quantitative understanding of the underlying processes and provides valuable experimental data for model development to guide safe biomass storage systems.

Suitable municipalities for biomass energy use in Colombia based on a multicriteria analysis from a sustainable development perspective

Using renewable energies is a global strategy to mitigate the acceleration of global warming generated by industrial processes and is a sustainable way to diversify the energy matrix in all countries. Biomass is a renewable energy source that produces biofuels and generates electricity and heat. The primary purpose of this work is to identify the municipalities in Colombia where agricultural, livestock, and urban residual biomass could be suitable for energy generation in a sustainable and renewable way. To that end, we carried out a Geostatistical Multi-Criteria Decision Methodology using Analytical Hierarchy Processes such as Rank-Sum and Weighted Linear Combination, as well as considering a set of sustainable development indicators applied to official Colombian data. Two scenarios are considered for comparison purposes. The first one is according to expert criteria, and the second one considers The Sustainable Development Goals proposed by the United Nations. Under both proposed scenarios, 127 municipalities were found to be suitable for agricultural-urban residual biomass and 162 for livestock-urban residual biomass for energy generation. One of the main limitations for the use of urban biomass is that municipalities need to have sufficient production potential to fulfill their own energy needs. An additional comparison with previous works to evaluate the performance of the Multi-Criteria Decision Methodologies MCDM is also proposed.

Acid and alkali pretreatment of agro by-products: Evaluating torrefaction efficiency and dechlorination

Utilisation of crop residues is limited due to their low energy and high ash content. This study aimed to develop a method for enabling the use of residual agricultural biomass through acid or alkali pretreatment followed by torrefaction. Pepper stems were treated with hydrochloric acid or sodium hydroxide for a brief period of time and rinsed with distilled water. Untreated and acid-pretreated samples had cellulose contents of 43.85% and 36.57%, respectively. The lignin content in the alkali-pretreated samples (22.74%) was lower than that in untreated samples (27.40%). Mass yield decreased with torrefaction temperature, ranging from 86.19% to 49.89%. However, alkali-treated samples showed smaller changes in mass yield (70.31–60.43%) than other samples. Regarding calorific value, untreated samples exhibited the highest increase (26.37%), whereas alkali-treated samples showed a modest increase of 10.62%. Chlorine content was higher in acid-compared with alkali-treated samples but decreased with temperature. Our study demonstrated that agricultural by-products can be used as energy sources through acid or alkali pretreatment prior to torrefaction. Future studies should explore a variety of agricultural by-products and consider pretreatment with different acids or alkalis, such as sulfuric acid and potassium hydroxide.

Efek Residu Biochar Sekam Padi terhadap Pertumbuhan dan Hasil Kedelai

&lt;p&gt;Biochar is a carbon-rich solid material derived from the pyrolysis of agricultural residue biomass, which takes longer to decompose than the raw material biomass. Biochar has been observed to have agronomic benefits. Because of its persistence in the soil, biochar has the potential to extend its agronomic benefits. The purpose of this study was to obtain evidence that biochar has a longer effect so that its residual effect can increase the growth and yield of soybean. A series of pot experiments which included 4 consecutive plantings were carried out. The treatments consisting of: control; rice husk biochar (RHB) 20 ton.ha&lt;sup&gt;-1&lt;/sup&gt;; RHB 40 ton.ha&lt;sup&gt;-1&lt;/sup&gt;; RHB 50 ton.ha&lt;sup&gt;-1&lt;/sup&gt;; RHB 60 ton.ha&lt;sup&gt;-1&lt;/sup&gt;; RHB 10 ton.ha&lt;sup&gt;-1&lt;/sup&gt; + chicken manure (CM) 10 ton.ha&lt;sup&gt;-1&lt;/sup&gt;; RBH 20 ton.ha&lt;sup&gt;-1&lt;/sup&gt; + CM 20 ton.ha&lt;sup&gt;-1&lt;/sup&gt;; RHB 30 ton.ha&lt;sup&gt;-1&lt;/sup&gt; + CM 30 ton.ha&lt;sup&gt;-1&lt;/sup&gt;. The treatments were applied to the first planting of the series experiment (September-December 2018). To determine the residual effect of the treatments, the second experiment was carried out in February-June 2019 with planting aerobic rice plants, third experiment in March-June 2020 with soybeans plant, and fourth experiment in July-October 2020 with soybean plants. The results showed that the effect of residual rice husk biochar did not significantly increase growth and soybean yields in the 3&lt;sup&gt;rd&lt;/sup&gt; and 4&lt;sup&gt;th&lt;/sup&gt; planting.&lt;/p&gt;

Effect of Agricultural Biomass Residues on the Properties of Recycled Polypropylene/Polyethylene Composites.

The aim of the study was to assess the usefulness of agricultural biomass residues as reinforcement in recycled polymer matrices. In this study, recycled polypropylene and high-density polyethylene composites (rPPPE) filled with three types of biomass residues, sweet clover straws (SCS), buckwheat straws (BS) and rapeseed straws (RS), are presented. The effects of the fiber type and the fibers content on the rheological behavior, mechanical properties (including tensile, flexural and impact strength), thermal stability and moisture absorbance were determined, in addition to morphological analysis. It was revealed that the addition of SCS, BS or RS increased the materials' stiffness and strength. The reinforcement effect increased as the loading of the fibers was increased, especially for BS composites in the flexural test. After the moisture absorbance test, it was found that the reinforcement effect slightly increased for the composites with 10% fibers but decreases with 40% fibers. The results highlight that the selected fibers are a feasible reinforcement for recycled polyolefin blend matrices.

Modelling of Electric Power Generation Plant Based on Gas Turbines with Agricultural Biomass Fuel

To ensure the survival of society, an enormous amount of energy is required to sustain the economic and social development of communities. In addition, there is a pressing need to achieve significant reductions in climate change and the associated costs of implementing systems based on traditional energy sources, as well as addressing the issue of providing electricity to isolated areas. In rural environments, there is an alternative energy source with enormous potential, agricultural biomass, which can produce electrical and thermal energy and can progressively help to reduce dependence on fossil fuels. The purpose of this work is to present a dynamic simulation model of a power generation plant that uses the Joule Brayton thermodynamic cycle, based on a gas turbine which is fueled by residual agricultural biomass; the cycle converts mechanical energy to electrical energy. The problem is approached through the characterization of the biomass, mathematical models of the plant components, and simulation of the system behavior in different scenarios. The simulations are processed in Matlab/Simulink, which allows the model to be verified, validating the equilibrium relationship between generation and load demand.

Design And Fabrication of Experimental Manufacturing of Pellets from Waste Material

Many developing countries produce huge amount of agro waste. The disposal of this waste is a major problem. The residues like wheat and rice husk, sawdust from carpentry shops, groundnut shells, and dry leaves from plants are available in a large quantity. Apart from the problems of storage, transportation and easy handling of this waste, burning of biomass in grates poses a greater problem of widespread air pollution. Biomass pellets are a well-liked sort of biomass fuel, generally made up of wood wastes, agricultural biomass, commercial grasses and forestry residues. In addition to savings in transportation and storage, pelletization of biomass facilitates easy and price effective handling. Dense cubes pellets have the flow ability characteristics almost like those of cereal grains. The even geometry and structure of biomass pellet helps in automatic feeding. Densely packed biomass pellets help in good durability in transport and storage. Pellets if densely packed and the moisture content is low the combustible properties can be increased. Keywords: Solar Energy, Wind Energy, PV Cell, Renewable Energy, Hybrid Power System, Electricity.

Reducing energy poverty in small rural communities through in situ electricity generation

Energy is key in achieving sustainable societies. There have been great efforts towards improving energy access worldwide. Despite the advances in energy access, energy poverty remains a major problem in many parts of the world, particularly in rural communities. Modern energy, in particular electricity, can help rural communities develop through improving education and health. During the last two decades, there have been improvements on bioenergy technological innovations, e.g. electricity generation from bioenergy from residual biomass from several agricultural crops in biorefineries. Most research has focussed on large biorefineries, with limited research on small-scale gasifiers’ location and contribution to energy poverty. This paper is aimed at assessing technological options to generate electricity in situ from biomass to reduce energy poverty of rural communities. This is done using four analysis methods: (1) crops availability data; (2) poverty and marginalisation data; (3) electricity provision/distribution; and, (4) GIS/Geographical latitude and longitude to locate municipalities in Mexico. The results shows that the generating potential for electricity using residual biomass with gasifiers could improve the welfare of almost 10 million people communities using residual biomass from crops harvested in such communities. This research provides location solutions on the best places to locate small-scale biorefineries. The research also provides systemic analysis to reduce energy poverty through in situ electricity generation using cheap accessible small plant technologies and biomass as raw material, as well as their location. Generating electricity in a decentralised way through agricultural residual biomass can help lift rural communities from poverty and improve their well-being, and, thus, make societies more sustainable.

The Development of Empirical Correlations to Understand the Frictional Behavior of Aqueous Biomass Slurry Flows in Vertical Pipes

Highlights The frictional pressure drop correlation of agricultural residue-water slurry flows in vertical pipes is developed. Multiple linear regression with the backward elimination method was used in RStudio to obtain the optimal model. Some regression coefficients differ for different types of biomass feedstocks. The predicted pressure drops agree well with the experimental data within a 95% CI. Empirical models for the onset velocity of drag reduction of different particle sizes of biomass are proposed. Abstract. Large-scale biofuel production at levels equivalent to conventional oil refineries using long-distance pipeline hydro-transport of biomass can be a cleaner alternative to fossil fuels when it comes to economics and traffic congestion associated with the overland transportation of biomass. The transport of aqueous slurries of several saturated mass concentrations (5%-40%) and four particle sizes (from &amp;lt;3.2-19.2 mm) of two types of agricultural residue biomass (ARB) feedstock (corn stover and wheat straw) was studied through a vertical test section of a 29 m long, 50 mm diameter closed circuit pipeline facility, and frictional pressure drops were recorded at different flow rates (0.5-4.3 m s-1). A framework was developed in RStudio (4.0.5) to analyze the experimentally obtained frictional pressure drops of biomass slurries through a multiple linear regression approach using a backward elimination method and Akaike information criterion. An empirical model was proposed to predict slurry frictional pressure drop in terms of slurry velocity, slurry solid mass concentration, particle aspect ratio, and feedstock type. The model satisfactorily predicted the frictional pressure drops of both feedstocks of biomass-water slurry flows through pipes within a 95% confidence interval. The correlations introduced for onset velocities of drag reduction in terms of slurry solid mass concentrations seemed helpful to interpret the transition points of the corresponding slurries in vertical upward flows through pipes. The empirical correlation developed in this research could help select biomass slurry pumps and pipe dimensions when designing a typical long distance pipeline network for biofuel production at the commercial level. Keywords: Agricultural biomass wastes, Frictional loss prediction, Numerical model, Onset velocity correlation, Regression coefficients, Upward pipe flow.

Research on Energy Metering System Based on Biomass Gasification Coupled Power Generation in a 600MW Power Plant

The biomass gasification coupled power generation project of a power plant is the first biomass gasification and coal-fired coupled power generation project using agricultural and forestry biomass residues as the main fuel in China, and has completed 72+24 hours of full load test run in September 2018. With the formulation of relevant standards, in order to further improve the overall operational capacity of the project, and give full play to the demonstration significance of the national coal-fired coupling power generation technology transformation pilot project, scientific and technological research has been carried out in such aspects as electricity metering. By upgrading the electricity metering system, on the one hand, it can meet the latest technical requirements of the electric power industry standard “Coal fired coupled biomass power generation biomass energy calculation Part 1: Agricultural and forestry waste gasification coupling”, on the other hand, it can solve the problems encountered in existing equipment such as short operation time, large maintenance volume, and low accuracy of gas composition detection, improving equipment stability, while reducing heat value loss, and reducing production costs, Improve production efficiency.At the same time, after the heat value analyzer is changed, the measured heat value loss is reduced by 20%. Based on the annual utilization hours of the gasifier, about 6400 tons of biomass fuel loss can be recovered in one year, and the annual fuel cost recovered is about 2.56 million yuan.

Optimization of Organosolv Pretreatment with Acid Catalyst to Enhance Enzymatic Saccharification of Corn Husk

Due to awareness of global warming and the devastation of environmental resources, the management of agricultural residues after each harvesting season has been integrated into the biorefining process to increase its value and mitigate environmental pollution caused by burning or combustion. This research focuses on the process development to utilize agricultural biomass residues for renewable energy production in the form of bioethanol. The study employed organosolv pretreatment with sulfuric acid as a catalyst to promote the enzymatic conversion of corn husk into reducing sugars. To determine the optimal conditions for the process, a one-factor-at-a-time method was initially employed to assess the influence of temperature (80-140 ºC), time (40-60 min), and sulfuric acid concentration (0.01-0.5% w/w). Subsequently, Response Surface Methodology (RSM) was conducted based on the Box-Behnken design (BBD) to identify the optimal pretreatment conditions. The predicted optimal pretreatment conditions were found to be 135.4 ºC, 57 min, and 0.46% w/w, resulting in a reducing sugar yield of 20.69% with a margin of error of 1.2%. Additionally, biomass composition analysis and Fourier Transform Infrared spectroscopy (FTIR) were performed to decipher the mechanism of organosolv pretreatment on enzymatic saccharification. This study demonstrated the potential of corn husk as an alternative raw material for the production of value-added products like bioethanol. The obtained reducing sugars serve as vital substrates for the fermentation process required to produce bioethanol as an alternative fuel to meet the target of sustainable development goals (SDGs).

Investigating biochar as a net-negative emissions strategy in Colombia: Potentials, costs, and barriers

Biochar is identified as a land-based mitigation technology (LMT) and a net-negative emissions technology (NET) with significant potential for mitigating climate change and providing co-benefits. Transforming residual biomass into biochar can potentially avoid CO2 emissions to be rapidly released to the atmosphere. This study aims to assess the sustainability of biochar production in Colombia as a NET. The research consists of five steps, literature review, expert elicitation, estimation of agricultural residues for biochar production, evaluation of biochar's CO2 mitigation potential, and techno-economic analysis of biochar under different biomass availability and technologies scenarios. Our findings indicate that approximately 10% of agricultural residual biomass can be transformed into biochar and reintegrated into the soil. Over a 100-year period, each tonne of biochar in the soil has the potential to avoid emissions of 1 to 2.2 t of CO2eq. Cost-wise, biochar production cost structure depends on the pyrolysis technology used. The cost structure of biochar production depends on the pyrolysis technology used. We find that raw feedstock represents the main cost component, ranging from 64% to 74% of total costs for artisan-made equipment, and 33% to 34% for specialized pyrolysis equipment. Capital investments, fixed costs, and raw feedstock account for the remaining costs. Our results highlight that the net present value (NPV) is most sensitive to biomass transport distance, biomass price and biomass humidity. Our findings can be used internationally for navigating the production, mitigation potentials, costs, and barriers of biochar, and devising deployment and market creation strategies.

Residual Lignocellulosic Biomass in the Production of HMF

5-Hydroxymethylfurfural (HMF) can be obtained from the dehydration of monosaccharides present in biomass, which helps add value to the raw material. The present work sought to study the relationship between the parameters of biomass characterization, including the content of reducing sugars, total soluble solids and the mid-infrared (MIR) and near-infrared (NIR) spectra, and the formation of HMF after synthesis. A thorough analysis was conducted in order to evaluate the residual agricultural biomass samples from sugarcane bagasse, corn stover, cassava branch, banana pseudostem and mango fruits after the drying (45 ºC maximum) and ball mill grinding pre-processing procedure. HMF synthesis was performed using 0.50 mol L-1 HCl and n-butanol as extracting solvent. The analytical quantification of HMF and furfural (co-product of synthesis) was performed using high-performance liquid chromatography coupled to diode-array detector (HPLC-DAD). The highest efficiency of the synthesis of HMF was observed for the mango fruits (55.0 kg ton-1) and sugarcane bagasse biomass (47.5 kg ton-1) samples. The application of data fusion and principal component analysis (PCA) allowed us to identify the samples with greater potential for HMF synthesis.

Residual Effect of Rice Husk Biochar on Growth and Yield of Aerobic Rice

Biochar is a carbon-rich solid material made by pyrolyzing agricultural residual biomass, and it decomposes much more slowly than the biomass from which it is made. Biochar has been shown to have agronomic benefits. Biochar can provide agronomic benefits for a longer period due to its persistence in the soil. The purpose of this research is to gather evidence demonstrating that biochar has a longer effect on increasing aerobic rice productivity. A pot experiment was carried out in UNINUS. The treatments were as follows: control, 20 Mg rice husk biochar (RHB), 40 Mg RHB, 50 Mg RHB, 60 Mg RHB, 10 Mg RHB + 10 Mg composted poultry litter (CPL).ha&lt;sup&gt;-1&lt;/sup&gt;, 20 Mg RHB + 20 Mg CPL.ha&lt;sup&gt;-1&lt;/sup&gt;, 30 Mg RHB + 30 Mg CPL.ha&lt;sup&gt;-1&lt;/sup&gt;, and 30 Mg RHB + 30 Mg CPL.ha&lt;sup&gt;-1&lt;/sup&gt;. Treatments were started in September 2018, and the effects were measured from February to June 2019. The findings revealed that rice husk biochar and its combination with CPL increased aerobic rice growth (plant height, number of tillers, and yield). The most effective combination rate is the application of biochar and composted poultry litter, 20 Mg RHB + 20 Mg CPL.ha&lt;sup&gt;-1&lt;/sup&gt;, because it significantly extended the residual effect. The combined application increased rice productivity when compared to a single application of biochar and composted poultry. The residual effect of biochar and composted poultry litter on rice productivity was superior to fresh application.

Biostimulants Using Humic Substances and Plant-Growth-Promoting Bacteria: Effects on Cassava (Manihot esculentus) and Okra (Abelmoschus esculentus) Yield

Traditional agriculture represents the most-extensive food-producing segment in the world. However, these agroecosystems are widely and closely associated with rural poverty, reflecting the dualism between the subsistence and the commodity-producing sector in the peripheric countries. Therefore, socially adapted technologies may be a reliable and helpful methodology to enhance subsistence crop production. Humic substances are natural organic biostimulants extractable as water suspensions from renewable sources such as agricultural biomass and farming residues. These easy-to-handle extracts may be mixed with plant-growth-promoting bacteria (PGPB) and used as biostimulants within a low-cost technological application in the circular economy strategy. Few investigations have been focused on the use of biostimulant practices on marginal or subsistence crops. Cassava (Manihot esculenta Crantz) and okra (Abelmoschus esculentus) are two essential foods for poor communities of rural territories in tropical and subtropical countries. The aim of this study was to evaluate the effect of the foliar application of a humic/PGPB mixed biostimulant on cassava and okra crops grown in an agricultural soil with very low natural fertility. In pot trials, the applied biostimulant improved the plant development with a 200% increase of the root weight in cassava, while the preservation of active diazotrophic bacteria was improved by 10- and 100-times in cassava and okra in the mixed formulation with humic acid. In real field systems, the plant treatment increased the yield of cassava and okra by 70% and 50%, respectively thereby allowing a simultaneous nitrogen savings with the best yield performance obtained at the lower N fertilization rate. The use of biostimulants can play a role in the transition process, helping the food security and the autonomy of impoverished farmers. Combining the elements of traditional knowledge and modern science is essential to create innovative technologies enabling the sustainable management of agroecosystems.