Dairy Sludge Research Articles

Evaluation of Monascus purpureus fermentation in dairy sludge-based medium for enhanced production of vibrant red pigment with minimal citrinin content.

This study aimed to explore the production of red pigment from Monascus purpureus in waste culture medium and its potential health benefits. Subsequently, the M. purpureus cultivated in a medium containing dairy sludge as waste, the extracted pigment was purified, and subjected to various analyses, including liquid chromatography mass spectrometry (LCMS) and nuclear magnetic resonance (NMR) to verify its purity, high-pressure liquid chromatography (HPLC) to measure the citrinin levels, microbial, and antioxidant activity. Finally, fermentation was conducted in a batch system using a fermenter. M. purpureus was grown in a medium composed of dairy sludge, monosodium glutamate, and glucose, resulting in a biomass yield of 26.15 g/L. After extraction and purification, the sample yielded 4.85 g of dry color. Analysis confirmed the purity of the pigment by LCMS and NMR and revealed low citrinin levels by HPLC. In the fermenter, the sample obtained from enriched culture conditions displayed the highest concentration of monascorubramine, maximum specific growth rate of 0.029/1/h, a cell yield (Yx/s) of 0.29 g/g, and a production efficiency of 65% for M. purpureus. The produced pigment sample showed potential for use in the food industry due to its low citrinin content and high concentration of red pigment.

Dairy sludge characteristics and its degradation during thermal treatment and thermal plasma treatment

ABSTRACT Thermal treatment and thermal plasma treatment processes of dairy sludge were conducted. The thermal treatment was undertaken at temperatures from 200 °C to 1000 °C to establish the chemical composition and thermal degradation of the sludge. These results served as a foundation for interpreting the properties of the vitreous slag obtained from the sludge treated in the DC-transferred arc plasma reactor. The dairy sludge is characterised by a high volatile matter but also presents substantial ash content, with primary elements such as Al, P, Si, Ca, and Fe. The characterisations of the samples were made employing techniques like X-ray fluorescence, X-ray diffraction analysis (XRD), FT-IR spectrometry, Thermogravimetric analysis, and Differential Scanning Calorimetry. The results highlight the degradation of primary milk components like lactose, casein protein, and milk fat, with distinct differential thermogravimetric peaks at 230, 316, and 479 °C. As the temperature of thermal treatments approached 1000°C, silicon dioxide, calcium silicon, dicalcium silicate, and hydroxyapatite were identified in XRD spectra. Plasma-treated sludge features various oxide crystalline structures, including Al2O3, CaO(Al2O3)6, CaO(Al2O3)2, Ca2Al(AlSi)O7, KFeO2, and ZrO1.98. FTIR analysis of sludge identifies a complex organic composition presenting alkanes, amines, amides, hydroxyl groups, and metallic and semi-metallic oxide bond absorption. The FTIR results suggest the degradation of organic compounds and retention of phosphorous and aluminum bonds, especially after 600 °C. The vitreous slag from plasma treatment exhibits distinct composition characteristics without organic compound, presenting a vitreous and metallic/ceramic matrix. This research underscores the potential of thermal plasma treatments to neutralise dairy sludge.

Optimization of anaerobic filter reactor with zeolite immobilization media for dairy sludge waste treatment for biogas production

Abstract Sludge from the dairy industry’s wastewater treatment contains a high organic content and a strong odor. It is proposed to treat the sludge by an anaerobic digestion process using a continuous anaerobic filter reactor (AFR) equipped with media immobilization support and a combination of ORP and pH sensors. Three immobilized media were put into different AFRs. The process took place in a cylindrical reactor with a column height of 150 cm and diameter of 63 cm with a total volume of 30 L. The total period of the anaerobic digestion process took place 17 days after the batch process. When the experiment was carried out using a flow-rate of 5 L/day, the highest sCOD removal of 90.44 % was using bioring media. Meanwhile, using flow-rate of 8L/day the highest sCOD removal up to 88.05 % was achieved by using zeolite media. The highest average methane production was obtained 8 mL/day and 24 mL/day of zeolite media by using flow-rate 5 L/day and 8 L/day respectively and reduced HRT up to 90 hours. To ensure the cellular activity on degradation of organic compounds is measured by Oxidation Reduction Potential (ORP) value. In the first stage, the ORP value is -60.23 mV to -472.82 mV for a flow-rate of 5 L/day subsequently the second stage is -471.9 mV to -477.75 mV for a flow-rate of 8 L/day. Anaerobic filter reactors using zeolite media can retain the effect of influent perturbation with a high range of alteration of sCOD and high recovery.

Biodiesel production, calcium recovery, and adsorbent synthesis using dairy sludge

Dairy sludge (DS) consists of organic compounds such as lipids and valuable inorganic elements. Biodiesel recovery from dairy sludge extract (DSE), using conventional acid (trans)esterification yielded only 16.5 wt%. In contrast, non-catalytic (trans)esterification generated a substantially higher biodiesel yield of approximately 74.0 wt% due to the method’s tolerance for impurities. Defatted dairy sludge (DDS) contained a higher Ca concentration than DS. DDS-produced biochar (DDSB) increased its Ca concentration predominantly in the form of CaO. 91.1% of the Ca was recovered from the DDSB containing Ca. The Ca remaining in the biochar residue (DDSBR) after Ca recovery was in the form of CaCO3. The porous structure developed as the Ca dissolved, implying that DDSBR could be an effective pollutant adsorbent. In this study, a method is proposed to maximize the utilization of DS by producing biodiesel, recovering Ca content, and using it as a pollutant adsorbent.

Bio-synthesis, purification and structural analysis of Cyclosporine-A produced by Tolypocladium inflatum with valorization of agro-industrial wastes

Cyclosporine A (CyA) holds significant importance as a strategic immunosuppressive drug for organ transplant patients. In this study, we aimed to produce pure and cost-effective Cyclosporine A (CyA) by fermenting a culture medium containing dairy sludge, using Tolypocladium inflatum PTCC 5253. Following the fermentation stage, ethyl acetate extraction and fast protein liquid chromatography were employed for sample purification. The initial evaluation of the effectiveness of CyA obtained from these processes was performed through bioassay, wherein the antimicrobial clear zone diameter was found to be larger compared to the sample obtained from the fermentation culture. The concentration of CyA was determined using high-performance liquid chromatography, yielding values of 334 mg/L, 456 mg/L, and 578 mg/L for the fermented, extracted, and purified samples, respectively. Further analysis utilizing liquid chromatography tandem mass spectrometry (LC/MS/MS) confirmed a purity of 91.9% and proper agreement with the standard sample based on the ion intensity of Z/m 1205. To validate the structure of CyA, nuclear magnetic resonance spectroscopy, Fourier-transform infrared (FT-IR), and Raman spectroscopy were employed. X-ray diffraction and differential scanning calorimetry analyses demonstrated that the purified CyA exhibited a crystal structure similar to the standard sample, characterized by two broad peaks at 2θ = 9° and 20°, and comparable glass transition temperatures (57–68 °C for the purified sample; 53–64 °C for the standard sample). Dynamic light scattering analysis confirmed a uniform particle size distribution in both the purified and standard samples. The zeta potentials of the purified and standard samples were determined to be − 25.8 ± 0.16 and − 23.63 ± 0.12 mV, respectively. Our results demonstrate that dairy sludge can serve as a suitable culture medium for the production of (CyA).

EXPERIMENTAL STUDY ON PHYSICOCHEMICAL PROPERTIES OF COMPOST BY PARTIAL REPLACEMENT OF ORGANIC MATTER WITH DAIRY SLUDGE

Organic wastes are wastes that are easily biodegradable. These wastes are produced from many sources such as agricultural waste, market waste, kitchen waste, urban solid food wastes and municipal solid waste. The main objective of the present study is to decompose the organic matter along with dairy sludge with different ratios through the Aerobic composting process, analyze the various controlling parameters during the process, test the physicochemical parameters of finished compost and compare it with the standards prescribed by AP Horticulture Department and to pick optimum dairy sludge and vegetative matter ratio and the benefits of this project were also discussed. In this study dairy sludge along with organic matter in four different ratios like 100% vegetative matter,40:60, 50:50, 60:40 was mixed for 15 days and allowed to decomposed for 45 more days and the finished compost physicochemical parameters were analyzed. Results from this study were compared with standards set for compost by AP horticulture department and the results of this study have met Standards fixed by Horticulture department. Although all the compost samples satisfied the required standards fixed by AP Horticulture department in terms of all physicochemical parameters sample 3 is found to best with dairy sludge to vegetative matter ratio of 50:50 was found to be best with Moisture content 20.91%, pH 7.4, EC 3.5dsm-1, Organic Carbon 22%, Nitrogen 1.6%, Phosphorus 0.78%, Potassium 0.91%, C:N ratio 13.75:1, Zinc 67.8 ppm, Iron 1420 ppm, Copper 14.20 ppm, and Manganese 31 ppm. In Sangam dairy an average of 600 KLD Wastewater was treated per day with assumed consistency of sludge as 1% and 120 mg/L suspended solids present in Wastewater and thereby leading to annual generation of 1248 ton of compost which generates an annual revenue of 62,40,000/- and an annual profit of about 50 lakhs excluding construction operation and maintenance costs. Key Words: biodegradable, Wastewater, compost, sludge

Hydrochar from dairy sludge as phosphorus fertiliser affects greenhouse gas emissions and maize yield

ABSTRACT Dairy processing sludge is a phosphorus (P) rich waste with a high potential to replace mineral phosphorus fertiliser in crop production, with possible enhancement of greenhouse gas emissions to the environment. Hydrothermal carbonisation is a technology that transforms the sludge into a hydrochar. The objective of this study is examining P availability of two hydrochars produced from Danish and Irish dairy sludge and their influence on greenhouse gas emissions and maize yields. The trial assessed (i) Danish dairy sludge; (ii) hydrochar derived from Danish sludge; (iii) hydrochar made from Irish dairy sludge; (iv) mineral phosphorus fertiliser; and (v) control. Emissions of nitrous oxide and carbon dioxide, soil pH, mineral nitrogen contents and crop yields were measured. Treatment with Danish dairy sludge had significantly higher cumulative nitrous oxide emissions while the emissions from both hydrochars were not significantly different compared to mineral phosphorous feriliser. Statistical modelling showed that temperature, soil nitrate content, interactions both between temperature and precipitation, and between soil moisture and precipitation were drivers for nitrous oxide emissions. There was no difference in emissions among all treatments when scaled for yield. Hydrochar may alleviate the enhanced nitrous oxide emissions in soil without constraining P availability and maize crop yields.

Experimental investigation on sludge conditioning and dewatering using an agricultural biomass coupled with resource recovery

In this study, the effect of modified areca husk fibre biochar (MAFB-AlCl3) on dairy sludge conditioning and dewatering along with raw and modified coconut shell biochar (MCSB-FeCl3) was investigated. Further, MgO impregnated biochars of areca husk fibre and coconut shells was carried out to evaluate the performance on phosphate recovery from the diary sludge. The enhancement in sludge dewatering with MAFB-AlCl3 were evaluated experimentally and significant reduction of capillary suction time (CST) (51.6 %), moisture content (18%), zeta potential (1.3 mV) and increased settleability (32.7%) were observed. The sludge conditioning parameters namely dosage (% of dry solids (DS)), rapid mixing time (RMT), slow mixing time (SMT) were optimized by response surface methodology for the modified biochars. Optimum CST (31.51 s) was obtained at dosage (50 % of DS), RMT (9.89 min) and SMT (17.23 min). Results of batch study for phosphate recovery by MgO impregnated biochars (MgB) was found to be 96.6 % and 100 % by MgB of areca husk fibre (MgAFB) and coconut shells (MgCSB) respectively. The morphological characteristics and elemental distribution using field emission scanning electron microscopy (FE-SEM) & energy dispersive X-ray spectroscopy (EDS) reveals the structural change in the sludge particles for the modified biochars as well as for sludge. Hence MAFB-AlCl3, MgAFB and MgCSB is proved to be suitable and an effective candidate for sludge conditioning and dewatering coupled with phosphate recovery in handling the diary sludge.

Optimization of dairy sludge fermentation culture medium to produce extracts containing bioactive peptides using co-culture of Limosilactobacillus fermentum and Saccharomyces cerevisiae

In this study, the general goal is to optimize the production of cell-free culture extract (CFC) containing bioactive peptides by co-cultivation of Limosilactobacillus fermentum and Saccharomyces cerevisiae in whey sludge bed and to investigate its biological properties. Temperature, time, and type of inoculation were considered as variables to optimize wet biomass production using the response surface method (RSM), and tests of ACE inhibitory activity, antioxidant activity, antimicrobial activity, proteolytic activity, and cell viability were performed on CFC prepared from the optimal treatment. The results of the central composite design (CCD) showed that the highest wet biomass production occurred at 34.86 °C with simultaneous inoculation for 43.1 h. The results obtained from CFC tests show the highest antimicrobial activity against Staphylococcus aureus and the highest DPPH radical activity of about 79.89 %. The value of IC50 in cytotoxicity assay against HT-29 cancer cells was 80.17 mg/mL.

Conversion of dairy sludge into biodiesel via Non-Catalytic transesterification

Considering the current energy infrastructure utilizing renewable energy that is compatible with it will be advantageous. From the perspective of compatibility, the use of biodiesel is promising. Although practical implementation and commercialization of biodiesel have been prioritized, the valorization of dairy sludge into biodiesel via conventional conversion protocols (acid-/base-catalyzed (trans)esterification) has not yet been realized. Tolerance against free fatty acids (FFAs), saponified fatty acids (SFAs), and undefined impurities in acid-/base-catalyzed (trans)esterification are vulnerable. To overcome the technical inferiority of acid-/base-catalyzed (trans)esterification, this study adopted non-catalytic (trans)esterification, which can valorize dairy sludge into biodiesel with high efficiency in a reaction time of ≤ 1 min. The non-catalytic conversion platform used in this study is invulnerable to impurities, and its reaction kinetics are governed by the temperature. Biodiesel recovery by non-catalytic (trans)esterification ranged from 72 to 75.8 wt% of dairy sludge extracts at 380 ℃. One of the interesting findings is that biodiesel recoveries from non-catalytic (trans)esterification of dairy sludge extracts at ≥ 300 ℃ were nearly similar. This suggests that the yield of biodiesel was saturated at ≥ 300 ℃. From the perspective of the economic viability of biodiesel production, the direct conversion of dairy sludge into biodiesel without lipid extraction is desirable. Thus, non-catalytic (trans)esterification of the two dairy sludge samples was performed. Biodiesel recoveries from the two dairy sludge samples were 31.7 and 38.8 wt% at 380 ℃, respectively. This finding demonstrates the extraordinarily strong tolerance against impurities and technical superiority of the introduced biodiesel conversion platform.

Probiotic Bacillus strains inhibit growth, biofilm formation, and virulence gene expression of Listeria monocytogenes

This research aimed to evaluate the probiotic potential and anti-biofilm properties of Bacillus species isolated from dairy sludge, namely Bacillus subtilis GS3 (DS-1), Bacillus cereus BF2 (DS-2), Bacillus velezensis DM (DS-3), and Bacillus thuringiensis JB (DS-4). These strains exhibited tolerance to gastrointestinal fluids, bile salt, phenol, NaCl, and temperature variations. Moreover, they demonstrated notable cell surface hydrophobicity (70.80–89.30%), auto-aggregation (79.30–92.70%), and cholesterol removal (20.12–59.46%). Additionally, the strains displayed antioxidant activity and susceptibility to a wide range of antibiotics. The cell-free supernatants (CFS) of the strains exhibited inhibitory effects against Listeria monocytogenes ATCC 19115, with minimum inhibitory concentrations (MIC) observed at 12.5%, 25%, 25%, and 50% v/v for DS-1, DS-2, DS-3, and DS-4, respectively. The CFS also showed degradation and inhibition of L. monocytogenes biofilms, affecting adhesion, hydrophobicity, auto-aggregation, and exopolysaccharide production. Notably, DS-1 CFS suppressed the expression of genes associated with biofilm formation in L. monocytogenes, including those related to quorum sensing, virulence factors, and flagella. The antibacterial activity of CFS against L. monocytogenes was further confirmed by scanning electron microscopy. Particularly, the CFS of Bacillus spp., especially B. subtilis GS3, exhibited a strong inhibitory effect on the biofilm formation of L. monocytogenes.

Enhancement of biomethane potential of brown sludge by pre-treatment using vortex based hydrodynamic cavitation

Novel, non-thermal and economically benign pre-treatment process was developed for enhancing valorisation potential of brown sludge generated by dairy industry wastewater treatment plant (WWTP). Vortex-based hydrodynamic cavitation (HC) device was used to quantify influence of pretreatment by measuring biomethane potential (BMP) of untreated and treated brown sludge. Pre-treatment parameters, primarily, pressure drop and number of passes through the cavitation device were varied to quantify influence on BMP. BMP tests were performed at 39 °C containing 5% of total solids in each reactors using an automatic BMP measurement system containing 15 reactors with each volume of 500 mL fitted with overhead stirrer. HC treatment increased the soluble chemical oxygen demand (sCOD) by more than 25% which increased the BMP. HC treatment was able to push the BMP of treated sludge to more than 80% of the theoretical BMP. Volatile solids (VS) removal was more than 65%. Highest methane yield was 376 mL/g-VS of sludge. The methodology and results presented here show significant potential to valorise brown dairy sludge via vortex based hydrodynamic cavitation.

Optimization of fermentation culture medium containing food waste for l-glutamate production using native lactic acid bacteria and comparison with industrial strain

l-glutamate as non-essential amino acid is one of the most abundant amino acids in the body, which plays an important role in various cellular processes and commercially produced as an important industrial amino acid. In this study, the production of l-glutamate by three native Lactic Acid Bacteria (LAB) (Levilactobacillus brevis PML1, Lactiplantibacillus plantarum 1058 and Limosilactobacillus fermentum 4–17) was optimized in culture medium containing dairy sludge and soybean meal using Central Composite Design (CCD) of Response Surface Methodology (RSM). Then, l-glutamate production was analyzed by chromatography and the characteristics of the fermented extract containing this amino acid were evaluated. The results of CCD showed that 500 mg/ml l-glutamate was produced under optimal conditions of 20% dairy sludge, 5% soybean meal, and 48 h of fermentation time (37 °C) at P < 0.05. The IC50 of the sample was 25 mg/ml that indicated proper antioxidant activity. The results of the fermented extract also showed acceptable antimicrobial, and toxicity properties (against cancer cells). Based on the obtained results, dairy sludge as a carbon source and soybean meal as a nitrogen source can be a suitable culture medium for the inexpensive production of l-glutamate.

Biohydrogen production: A new controllability criterion for analyzing the impacts of dark fermentation conditions

Biohydrogen production from renewable resources using dark fermentation has become an increasingly attractive solution in sustainable global energy supply. So far, there has been no report on the controllability analysis of biohydrogen production using dark fermentation. Process controllability is a crucial factor determining process feasibility. This paper presents a new criterion for assessing biohydrogen process controllability based on PI control. It proposes the critical loop gain derived via Routh stability analysis as a measure of process controllability. Results show that the dark fermentation using the bacteria from anaerobic dairy sludge and substrate source from sugarcane vinasse can lead to a highly controllable process with a critical loop gain value of 4.3. For the two other cases, an increase of substrate concentration from 10 g/L to 40 g/L substantially reduces the controllability. The proposed controllability criterion is easily adopted to assess the process feasibilty based on experimental data.

Reduced Climate Impacts of Dairy Sludge Management by Introducing Hydrothermal Carbonization

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Application of Post-Flotation Dairy Sludge in the Production of Wood Pellets: Pelletization and Combustion Analysis

The amount and variety of waste increases every year. One of the places where biodegradable waste is generated is the agri-food industry, where it is possible to utilize it for the purpose of energy production. The aim of this research was to determine the possibility of using post-floatation dairy sludge as a raw material for co-pelletization with sawdust. The scope of this work included physical and chemical characterizations of the feedstock, the co-pelletization process, and the combustion of the produced pellets, combined with an exhaust analysis. The obtained values of the pellets’ density at each level of sludge addition allowed us to conclude that the obtained pellets had a good market quality and constituted a full-fledged, innovative solid fuel, in accordance with the guidelines of the latest, currently applicable ISO 17225 standard. Furthermore, adding ca. 20%wt of sludge to sawdust resulted in a 30% decrease in the pelletization power demand, and still, the combustion characteristics of the pellets met the European Ecodesign emission limitations in terms of the CO and NOx content in the exhaust. The addition of post-flotation dairy sludge to sawdust has a beneficial influence on the production of fuel pellets by decreasing the energy consumption of the pelletization process and improving the pellets’ kinetic durability. Due to legal requirements and the pursuit of the circular economy principle, one should expect an increased interest in the use of agri-food waste for the production of biofuels.

Enhancement of alkaline protease production of Bacillus strains isolated from dairy sludge under cold, salt and ultrasound stress

Proteases make up two-thirds of all enzymes used in various industries. This study aimed to optimize the production of alkaline protease enzyme under stress conditions in Bacillus cereus strain zk2 and Bacillus thuringiensis strain ILBB224 isolated from dairy sludge. Protease activity was measured quantitatively based on released tyrosine during casein hydrolysis. Response surface methodology was used for the optimization of enzyme production. Results revealed that the optimal enzyme production yield can be achieved at 5 °C, 1 m KCl (the incubation medium is skimmed milk with 1 m KCl), and 20 kHz frequency of ultrasound for 1 min. Under optimal conditions, protease activities of zk2 and ILBB224 strains were 2.8 and 3.2 times higher, respectively, compared with the suboptimal conditions tested. Therefore, low temperatures, high concentrations of KCl, and short-time ultrasound stress appear to increase alkaline protease production by these strains.

Electrokinetic removal of aluminium and sulfates from a dairy sludge

ABSTRACT Electrokinetic (EK) treatment of soil/sludge contaminated with metallic and organic pollutants has proven its success concerning efficiency and cost. The study carried out in the laboratory aimed at the feasibility of this technology for the simultaneous elimination of aluminium and sulphates from sludge obtained from the clarification of industrial dairy wastewater by coagulation-flocculation with aluminium sulphate. Work in this area is scarce due to the presence of bacteria in the sludge. The EK reactor comprises three compartments: the anode, the cathode, and the central part, which contains the sludge to be treated. A constant voltage of 15 V is applied between two platinum wire electrodes immersed in each electrolytic compartment. The EK treatment employed gave satisfaction despite the bacterial front in the 3/5 of reactor sludge fractions. Indeed, the removal rates are approximately 72% for aluminium and 92% for sulphates with current values below 5 mA, and relatively low energy consumption and cost (648 kWh/ton and 25.9 $/ton of sludge, respectively). For EK transport, the absence of hydraulic convection exerted on the sludge would favour the displacement of aluminium and sulphates by electromigration. Electroosmosis also contributes to this displacement. Thereby, analysis of sludge after this EK treatment predicts a possible valorisation but after liming. The sludge is rich in nutrients with low heavy metals concentrations. Although the study is more interesting for aluminium because of its toxicity, the behaviour of sulphates suggests the possibility of using EK to decontaminate soils or sludge from anions like nitrates, chlorides, etc.

Phosphorus recovery as struvite from hydrothermal carbonization liquor of chemically produced dairy sludge by extraction and precipitation

Phosphorus (P) recovery from dairy wastewater involves its accumulation into phosphorus-rich sludge using a physico-chemical or biological process. The high iron content in chemical sludge decreases its usability in agricultural activities. The hydrothermal carbonization (HTC) is an option used to treat the sludge to obtain hydrochar for various applications, including its use as an energy source and as a carbon-dense material. The HTC process leaves a bigger volume of nutrient-rich liquor, which phosphorus (P) purification was the subject of this work. By direct precipitation, the product iron content was 17.96%, a value higher than accepted limits for phosphate fertilizers. Thus, P extraction followed by struvite precipitation was studied. The use of oxalic acid extracted 86.7% of P from HTC liquor, while 86.6% of iron was removed. The process conditions of pH 9, and salt dosage of 1.73:1.14:1 for Mg:NH4+:P mole ratio for struvite precipitation were obtained with a P recovery of 99.96%, and the effluent P concentration below 2 mg∙L−1. The quality of products as fertilizers was tested by both in-vitro and in-vivo assays. High iron content in the product demonstrated a negative effect on plant germination, whilst the precipitation product from P extract demonstrated an advantage of P purification into struvite for plant macro and micronutrient availability. The used method of P extraction followed by struvite precipitation is useful for both P and iron recovery into two separate products with agricultural and chemical applications, respectively.

Systematic Review of Dairy Processing Sludge and Secondary STRUBIAS Products Used in Agriculture

Worldwide dairy processing plants produce high volumes of dairy processing sludge (DPS), which can be converted into secondary derivatives such as struvite, biochar and ash (collectively termed STRUBIAS). All of these products have high fertilizer equivalent values (FEV), but future certification as phosphorus (P)-fertilizers in the European Union will mean they need to adhere to new technical regulations for fertilizing materials i.e., content limits pertaining to heavy metals (Cd, Cu, Hg, Ni, Pb, and Zn), synthetic organic compounds and pathogens. This systematic review presents the current state of knowledge about these bio-based fertilizers and identifies knowledge gaps. In addition, a review and calculation of greenhouse gas emissions from a range of concept dairy sludge management and production systems for STRUBIAS products [i.e., biochar from pyrolysis and hydrochar from hydrothermal carbonization (HTC)] is presented. Results from the initial review showed that DPS composition depends on product type and treatment processes at a given processing plant, which leads to varied nutrient, heavy metal and carbon contents. These products are all typically high in nutrients and carbon, but low in heavy metals. Further work needs to concentrate on examining their pathogenic microorganism and emerging contaminant contents, in addition to conducting an economic assessment of production and end-user costs related to chemical fertilizer equivalents. With respect to STRUBIAS products, contaminants not present in the raw DPS may need further treatment before being land applied in agriculture e.g., heated producing ashes, hydrochar, or biochar. An examination of these products from an environmental perspective shows that their water quality footprint could be minimized using application rates based on P incorporation of these products into nutrient management planning and application by incorporation into the soil. Results from the concept system showed that elimination of methane emissions was possible, along with a reduction in nitrous oxide. Less carbon (C) is transferred to agricultural fields where DPS is processed into biochar and hydrochar, but due to high recalcitrance, the C in this form is retained much longer in the soil, and therefore STRUBIAS products represent a more stable and long-term option to increase soil C stocks and sequestration.