Development of functional composts using spent coffee grounds, poultry manure and biochar through microbial bioaugmentation

Oil extracted from spent coffee ground (SCG) has been well known as a potential feedstock for high quality biodiesel production. This work was to investigate extraction, physical and chemical characterizations of Robusta coffee oil (CO) and its application for biodiesel production. Analysis of seven coffee ground (CG) samples showed that oil content in CGs depended on technique of the manufacturer. Morphological changes of CGs surface were recorded by FESEM technique which showed the particle size significantly increased with the oil loss. Infrared spectroscopies revealed absence of SCG oil in the de-oiled SCG, confirmed that soxhlet method in hexane was used efficiently for the oil extraction. Thermal properties of SCG oil, fresh coffee ground (FCG), SCG and de-oiled SCG samples were investigated by simultaneous TG–DTA measurement. The obtained data showed the oil content relating to thermal changes of SCG samples. Comparison between chemical components of Robusta coffee bean (RCB) and SCG reflected a fact that most of oil content in the SCG could be originated in manufacturing process of FCG. Quality biodiesel product has prepared from SCG oils via a two-step process. After pre-treatment process, transesterification of SCG oils was carried out with methanol (v/v, 30%) and NaOH (w/v, 1%) in yield 89.2%.

To maintain high production and growing rates of plants, synthetically obtained fertilizers are commonly used. Excessive amounts of fertilizers damage the natural ecosystem and cause various environmental problems. In relation to the environment and its sustainability, another great environmental, economic, and social issue is food loss and waste. This paper aims to evaluate the impact of spent coffee grounds (SCG) on soil properties, rye growth, and their possibilities to be used as the biodegradable and organic material in the production of organic bulk fertilizer. This study demonstrated that spent coffee grounds contain primary nutrients; moreover, SCG could increase the content of soil organic matter. The addition of 4 wt% to 8 wt% SCG increased the number of spore-forming bacteria from <103 colony forming units/g soil (CFU/g soil) to 3 × 104 CFU/g soil, along with nitrogen assimilating bacteria (plain soil resulted in 5.0 × 105 CFU/g, and addition of SCG increased the value to 5.0 × 107 CFU/g). Since spent coffee grounds have a relatively high porosity and absorbance (25.3 ± 3.4 wt% in a water vapor environment and 4.0 ± 0.6 wt% in the environment of saturated sodium nitrate solution), they could be used to reduce the amount of water required for irrigation. To fully exploit their nutritional value for plants, spent coffee grounds were mixed with green algae biomass along with urea, and, during the research, higher value products (organic bulk fertilizer) were obtained.

Spent coffee grounds (SCG) represent an environmental problem, although their composition makes them an interesting, re-valuable product to be incorporated in food. In this work, texture characteristics, proximate composition, total phenolic compounds (TPCs) content, and antioxidant activity were evaluated in cookies added with SCG (0.0, 10.0, 17.5 and 25.0 g/100 g). Intensity of specific sensory characteristics in cookies added with SCG was evaluated by 131 consumers using the just-about-right scale. Texture characteristics were not affected by SCG content. Crude fiber, fat, ash and TPC content increased with the increment of SCG in cookies (p < .01). All the cookies added with SCG were pleasant for consumers, although cookies with 17.5 g SCG /100 g were preferred (p < .05). Intensity of coffee flavor and granulosity seemed to determine its acceptance. Adding 17.5 and 25.0 g SCG/100 g in cookies allows to obtain a product acceptable for consumers, considered as dietary fiber source. Practical applications Spent coffee grounds (SCG) are considered an underutilized by-product by its high content of fiber and presence of antioxidant compounds. During development of functional foods, it is recommendable that the product shows an attractive composition, but also enjoyable sensory characteristics, which make it acceptable for consumers. Inclusion of SCG in cookies is a viable alternative for adding value to this by-product, reducing waste, and, at the same time, obtaining an interesting, functional food.

Although studies have shown that spent coffee ground (SCG) extracts have antioxidant activity, no systematic study has been reported under actual storage conditions. The purpose of this study is to estimate the feasibility of practical application of SCG extracts as natural antioxidants for soybean oil and fish oil. An ethanol extract (EE), an acetone extract (AE), and polar compounds isolated from oil (PCO) are prepared and their activity is compared to a synthetic antioxidant, butylated hydroxytoluene (BHT). EE shows the strongest radical scavenging activity for 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH) radicals and the highest total phenolic content (TPC) followed by AE and then PCO. However, during storage of soybean oil and fish oil at 35 and 50 °C, AE has the strongest antioxidant activity as determined by peroxide value, conjugated diene value, p‐anisidine value, and headspace volatile analyses. In soybean oil, 0.25% AE has antioxidant activity that is equal to or better than 0.02% BHT. In fish oil, the antioxidant activity of 0.25% AE is inferior to that of 0.02% BHT. However, increased concentrations of AE show improved antioxidant activity. This study shows that SCG extracts can be practically used as natural antioxidants for vegetable oils and omega‐3 oils.Practical Application: Due to lack of information about the antioxidant activity of spent coffee ground (SCG) extracts, this study is specifically aimed and designed to provide information on their activity toward soybean oil and fish oil during actual storage. This study shows that 0.25% acetone extract has equal or better protective effects than BHT in soybean oil at 35 and 50 °C. The activity is further improved with increasing concentration. The activity of the acetone extract in fish oil is not as strong as in soybean oil, but higher concentrations further improve the antioxidant activity. In this study, it is clearly demonstrated that the SCG extracts can have practical use as natural antioxidants for vegetable oils and oils with high concentration of omega‐3 fatty acids.Among spent coffee ground (SCG) extracts, the acetone extract (AE) has the strongest antioxidant activity. In soybean oil, 0.25% AE has antioxidant activity that is equal to or better than 0.02% butylated hydroxytoluene (BHT). This study shows that SCG extracts can be practically used as natural antioxidants for edible oils.

This paper presents an optimization study of spent coffee grounds (SCG) as cement mortar additives to enhance mortar strength. In recent years, sustainable materials have begun finding their way into cement mortar, with SCG being one. There is limited optimization study on the SCG addition in mortars, hence this study was performed to optimize the curing time and SCG addition in cement mortar to achieve the highest compressive strength through response surface methodology. Scanning Electron Microscopy (SEM) characterization was carried out on the SCG particles to identify their physical properties. An Energy Dispersive X-ray (EDX) analysis was carried out to identify its chemical properties. Simultaneously, a workability test, the flow table test, is conducted to study the effect of SCG on the flowability of the cement mortar mixes. The synergistic effect between SCG content in cement mortar mixes and the curing period was statistically studied and analyzed. Both parameters were then optimized to obtain the best performance mix of SCG in cement mortar. It was found that 1.1% SCG and a curing day of 68 days produced the highest compressive strength (33.4MPa) of cement mortar. The Response Surface Methodology (RSM)-optimized cement mortar mix presented at least a 12.62% improvement in compressive strength from control cement mortar without SCG additives (28.77MPa). Experimental validation of the optimum condition showed a good agreement with a deviation of 3.12% in three replicates, thus indicating that the optimum model in this work can be used to model the compressive strength of the SCG-cement mortar mixture.

Annually, up to 15 million tons of coffee production waste are produced worldwide. Among them are spent coffee grounds (SCG), which have the potential to be recycled and used as organic fertilizers. However, their direct application to soil is limited due to the presence of ecotoxic compounds (phenols, tannins, and caffeine). Composting is a promising approach; however, the highly variable properties of the raw coffee materials require the selection of optimal production and application modes. In this study, we performed two composting methods for SCG, i.e., vermicomposting and microbial composting, in mixtures with co-composting substrate at five SCG/substrate ratios (0, 25, 50, 75, and 100% SCG). First, the acute toxicity of raw SGC and its mixtures to earthworm Eisenia andrei was evaluated. After 30 days of composting, chemical and microbiological properties, including pH, RedOx potential (Eh), organic carbon (Corg), lignin content, bacteria count, diversity, and potential metabolic activity, were determined in the end products. As composting went on, the pH increased from 5.6–6.2 to 6.0–7.3 and 7.4–7.7 under microbial composting and vermicomposting, respectively. RedOx potential levels achieved 142–166 mV for microbial composting and 73–113 mV for vermicomposting. Organic matter (OM) content reached 86–94%, with an increasing proportion of lignin, demonstrating the decomposition of more readily accessible organic matter. Vermicomposting and microbial composting produced chemically safe and microbiologically highly active composts. An initial SCG content of 25–50% of the compost mixture’s weight yielded the most favorable properties for the resulting compost (high organic matter content and optimal pH levels). Due to the high biological activity of both composting methods, the resultant composts are likely to have a positive effect on plant growth and development and soil health when used as organic nutrient resources.

Physicochemical characterization and energy recovery of spent coffee grounds

Complete utilization of wet spent coffee grounds waste as a novel feedstock for antioxidant, biodiesel, and bio-char production

Most spent coffee grounds (SCGs), a byproduct of brewing coffee, are buried in landfill sites, and their decomposition produces significant greenhouse gases. As the recent warming of the Earth’s climate has made it imperative that industries reduce greenhouse gas emissions, the present study investigates the viability of recycling SCGs for use as a partial replacement of aggregates in concrete materials. Cement mortar samples with a fixed cement-to-water ratio and varying amounts of SCGs were fabricated and tested. Mechanical strength tests revealed that an appropriate amount of SCGs can improve compressive strength. However, since strength deterioration was also observed in samples with too much or too little SCG content, finding the optimal amount is necessary for implementation. The samples’ thermal conductivity decreased as the amount of SCGs increased, capturing the effective insulating substance of air within the SCGs’ porous structure. The increased insulating capacity of concrete materials resulting from the addition of SCGs could be beneficial in terms of a building’s lifecycle cost and carbon emissions. Thus, the SCGs once disposed of in landfills to emit greenhouse gases can be transformed into an appealing and eco-friendly building material if the proper concrete mix ratio is used.

&lt;abstract&gt; &lt;p&gt;Large amounts of solid wastes such as spent coffee grounds (SCGs) from brewing provide a valuable sugar source to investigate. The effects on the sugar properties of extraction factors were studied. Different solvent extractions using an autoclave showed distinguishable sugar contents and properties. Water extracted the highest total sugar content while alkali extracted the highest total phenolic content (TPC). The ultrasonic-water-bath-assisted extraction with water did not produce any significant content or TPC. Finally, the combination of ultrasonic-autoclave-assisted extraction with water at 40% amplitude for 10 min produced the highest total sugar content and TPC, similar to that found in samples from the autoclave extraction with water. The FT-IR spectra of SCGs sugar revealed both amorphous and crystalline structures. All sugar extracts from SCGs contained phosphorus, potassium and calcium as the main mineral elements. Thus, sugar extracts from SCGs can be considered as an alternative additive with a good TPC for food products.&lt;/p&gt; &lt;/abstract&gt;

EU countries are the most important worldwide coffee consumers with about 2.52 million tons. Coffee processing and consumption lead to substantial amounts of residues, mainly coffee silver skin and spent coffee grounds (SCG) as follows: 1 kg of coffee generates around 2 kg of wet SCG. Around 46% of this total SCG generation is landfilled with the subsequent soil, water and air pollution. So, an alternative solution for large SCG volumes currently sent to landfills is necessary. Livestock products are projected to increase up to by 70% by 2050. Many of the ingredients in the diets of EU livestock are sourced from imported raw materials from the Americas: mainly soybeans, etc. This deficit presents already a risk to social, economic and environmental progress in Europe due to the increasing scarcity of global resources. Hence, the inclusion of biowaste in animal feed is necessary to lead to additional benefits for animal feed sector: availability of environmentally friendly ingredient sources and decrease of dependence on foreign sources. This study demonstrates that coffee spent ground stands as a potential alternative ingredient in dairy cattle due to their availability in Europe, their nutritional characteristics and the results of the growing trials with animals: feeding of 5% SCG in the concentrate did not affect milk yields or fat contents and only a negligible decrease in crude protein (by 1.8%). This is because SCG was formulated as a functional ingredient in the concentrate and therefore would not impair animal performance.

Spent coffee grounds (SCG) are frequently disposed of in landfills, which creates significant environmental concerns. Scientists are investigating methods to repurpose SCG, recognizing its potential for various beneficial applications. This study compared oven and microwave drying methods for extracting oil from spent coffee grounds (SCG), focusing on yield and quality of oil. The findings demonstrated that oven drying resulted in a slightly lower moisture content and a significantly higher oil yield (10.01%) compared to microwave drying (8.9%). Additionally, oil from oven-dried SCG exhibited superior quality, with lower acid and peroxide values, indicating less oxidative degradation during the drying process. The structural analysis further supported these results, showing that oven drying better preserved the SCG's cellular structure, which may contribute to the higher retention of oil-bearing compounds. In contrast, microwave drying, while faster, caused more structural damage and led to lower oil yield and reduced quality due to its rapid heating mechanism. This research contributes to the growing body of knowledge on sustainable SCG utilization by highlighting the advantages of oven drying for optimizing oil extraction. The findings are particularly relevant for industries that prioritize oil quality and yield, such as cosmetics and pharmaceuticals.

Spent coffee ground as renewable energy source: Evaluation of the drying processes

Coffee consumption has been positively linked with a decreased risk of different diseases. The spent coffee ground, the product obtained after the brewing process, can be reused for its beneficial abilities. This work contributes to the investigation of the chemical composition of the hydroalcoholic extract of spent coffee (Arabica and Robusta) grounds, its antioxidant and antibacterial activities. The GC-MS analysis of the extract obtained by Soxhlet revealed the presence of 14 components such as curlone, octadecane, and dillapiol. Also, the major compound found in our extract, namely curlone, was not previously reported in spent coffee grounds. These compounds are known for their important biological activities. The extract was found to be rich in polyphenolic compounds, with a value of 129.43 ± 6.05 mg GAE/g extract. The DPPH assay revealed an important antioxidant IC50 value (11.95 ± 0.96 μg/mL). Also, the antibacterial assay performed by the Agar Diffusion Method showed that all tested bacteria were sensitive against the hydroalcoholic spent coffee grounds extract (HECG), especially Escherichia coli. Minimal inhibitory concentrations (MIC) as low as 2.5 mg/mL (Luteibacter sp.) were recorded against different bacterial strains. These results suggest that “HECG” is a potential source of important bioactive compounds.

The isothermal combustion characteristics of anthracite and spent coffee grounds briquettes in a bench-scale fixed-bed furnace were examined by using a macro-thermogravimetric analysis approach between 873 and 1173 K. The combustion performances in terms of the conversion rates, flame evolution, pollutant emissions, ash compositions and ash fusion temperatures of two anthracite/spent coffee grounds blend briquettes with blending ratios of 40% and 60% were also compared with those of their individuals. There was only an obvious peak in DTG profile for every sample at each temperature. At 973 K, the average burning rate of the spent coffee grounds was about 8 times higher than that of the anthracite. The average burning rate of 60% anthracite/40% spent coffee grounds blend at 1173 K increased by about 3 times in comparison with that at 873 K. NO2 emissions for the four samples were much less than other gaseous emissions. The four ash fusion temperatures for the anthracite were higher than 1791 K. The deformation temperature, softening temperature, hemispherical temperature and flow temperature for the spent coffee grounds were 1526, 1626, 1687 and 1791 K. The ash fusion characteristics of the spent coffee grounds were improved by blending the anthracite.