Integration of on-farm biodiesel production with anaerobic digestion to maximise energy yield and greenhouse gas savings from process and farm residues

Anaerobic co-digestion of residues from the cold pressing and trans-esterification of oilseed rape (OSR) with other farm wastes was considered as a means of enhancing the sustainability of on-farm biodiesel production. The study verified the process energy yields using biochemical methane potential (BMP) tests and semi-continuous digestion trials. The results indicated that high proportions of OSR cake in the feedstock led to a decrease in volatile solids destruction and instability of the digestion process. Co-digestion with cattle slurry or with vegetable waste led to acceptable specific and volumetric methane productions, and a digestate low in potentially toxic elements (PTE). The results were used to evaluate energy balances and greenhouse gas emissions of the integrated process compared with biodiesel production alone. Co-digestion was shown to provide energy self-sufficiency and security of supply to farms, with sufficient surplus for export as fuel and electricit

Behaviour of milk protein ingredients and emulsions stabilised by milk protein ingredients in the simulated gastrointestinal tract : a thesis presented in partial fulfilment of the requirements for the degree of Master of Food Technology, Massey University, Manawatu, New Zealand

Milk clotting behaviours in the stomach impact the digestion rates of protein and fat. A variety of milk protein products are applied as functional ingredients in many foods. This research was conducted to investigate the digestion behaviours of various commercial dairy ingredients and lipids in emulsions stabilised by these ingredients using a dynamic in vitro digestion model, i.e., a human gastric simulator (HGS), with a focus on the effect of different structures of clots formed in dairy ingredients during gastric digestion on hydrolysis of proteins and/or lipids. Skim milk powder (SMP), milk protein concentrate (MPC) 4851, MPC 4861, sodium caseinate, whey protein isolate (WPI) and heated (90°C, 20 min) WPI were used in the present study. Results showed that SMP and MPC 4851, which contained casein micelles, formed ball-like clots with a relatively dense network after 10 min of gastric digestion. These clots did not disintegrate after 220 min of digestion. MPC 4861 and sodium caseinate generated clots at around 40 min, and a loose, fragmented structure was observed at the end of the gastric digestion due to a lacking micellar structure of caseins. No clot was observed in WPI or heated WPI after 220 min gastric digestion, although aggregation occurred at around 40 min in heated WPI. These differences in coagulation behaviours apparently affected the rate of gastric emptying and protein hydrolysis by pepsin in the gastric system. In SMP and MPC 4851, the gastric emptying and hydrolysis of caseins was much slower than that observed in MPC 4861 and sodium caseinate. The most rapid gastric emptying of proteins was observed in the WPI samples both with and without heating. This is attributed to the formation of varied structured clots at different times under the gastric conditions. The effect of protein concentration on the gastric behaviour of these dairy ingredients in solution was then examined, with a particular emphasis on the structure of clots. SMP and MPC 4851 have been selected as model protein ingredients. Their gastric behaviours were investigated over a protein concentration range of 0.5-5.0% (w/w). The results showed that the digestion behaviour of SMP and MPC 4851 followed a similar pattern. The rate of pH changes in the emptied digesta during digestion was protein concentration dependent. With an increase in protein concentration, the decrease in pH slowed. The protein concentration had no apparent impact on the casein clotting time. Clots were formed in the first 10 min of digestion in all samples. However, in both SMP and MPC 4851, when protein concentration was lower than 2.0% (w/w) the clots consisted of small protein pieces with a loose, porous and open structure after a 220 min digestion. Whereas a cheese ball-like clot with a denser network was observed at the end of gastric digestion when the protein concentration varied from 2.0% to 5.0% (w/w). Such a difference in the structure apparently affected the rate of protein hydrolysis. A more rapid hydrolysis (P < 0.05) of the clotted protein was observed when protein concentration was lower than 2.0% (w/w) compared to the samples containing a higher proportion of protein (2.0%-5.0%, w/w). To study the effect of different coagulation behaviours on the digestion of oil droplets in oil-in-water emulsions, these dairy ingredients (with the exception of SMP) were used to prepare an oil-in-water emulsion (20.0% soy oil and 4.0% protein, w/w). They were digested under the dynamic gastric conditions using the HGS. The gastric digesta was emptied at 20 min intervals. Then all digesta were mixed to investigate the lipid digestion under the small intestinal conditions. Changes in physicochemical properties of emulsions, involving the particle size, the microstructure, the oil content of the emptied gastric digesta and the amount of free fatty acids (FFAs) released during the small intestine stage, were determined using an in vitro small intestinal digestion model. Aggregation of MPC 4851-stabilised emulsion took place after 5 min of digestion in the HGS with the largest size. The aggregates remained in the stomach and did not disappear during the whole gastric digestion. The hydrolysis of the aggregated network by pepsin was largely slowed by the reduced ability of the simulated gastric fluid (SGF, containing pepsin) to diffuse into the larger sized aggregates. MPC 4851-stabilised emulsion thus resulted in the slowest release of oil droplets into the small intestine. In comparison, MPC 4861 and sodium caseinate-stabilised emulsions aggregated in the stomach at approximately 40 min, forming smaller sized aggregates. These aggregates disintegrated at the mid and late-stages of digestion in these two emulsions. Therefore, MPC 4861 and sodium caseinate-stabilised emulsions had a more rapid delivery of oil droplets into the small intestine. In relation to the WPI-stabilised emulsions both with and without heating, the aggregations formed at a similar time to that which was observed in MPC 4861 and sodium caseinate-stabilised-emulsions; i.e., at approximately 40 min. However, they had the smallest sized aggregates amongst all samples and they disintegrated quickly with further digestion. WPI-stabilised emulsions both with and without heating had the fastest gastric emptying and hydrolysis by pepsin in the early and mid-stages of the gastric digestion process. Thus, the highest level of oil content contained in the emptied gastric digesta was produced from both WPI-stabilised emulsions. In the mixed gastric digesta, which were subjected to the small intestinal digestion, the oil contents contained in the different emulsion samples varied. This difference impacted the extent of lipid digestion by pancreatic lipase. The sample with a higher oil content released a greater amount of FFAs compared to the sample with a lower oil content. The extent of lipid digestion of different emulsion samples adhered to the following pattern: MPC 4851-stabilised emulsion < MPC 4861-stabilised emulsion < sodium caseinate-stabilised emulsion, WPI-stabilised emulsions both with and without heating. Overall, the gastric behaviours of dairy ingredients either in solutions or emulsions were affected by the formation of structured clots/aggregates. The differences in clotting/aggregation times and their structures were greatly dependent on the component and structure of protein, the processing prior to digestion and the susceptibility to proteases. These differences in protein coagulation/aggregation behaviour impacted the rates of protein hydrolysis and gastric emptying. The oil content and protein composition of the gastric digesta transferred into small intestine and the extent of lipid digestion in small intestine were also affected. These results are important in an application perspective. They provide useful information for the design and development of healthier food products by allowing greater control over the manipulation of protein bioavailability, which subsequently provides greater control over lipid metabolism

Effects of Replacing Dry-rolled Corn with Increasing Levels of Corn Dried Distillers Grains with Solubles on Characteristics of Digestion, Microbial Protein Synthesis and Digestible Energy of Diet in Hair Lambs Fed High-concentrate Diets.

Four male lambs (Katahdin; average live weight 25.9±2.9 kg) with "T" type cannulas in the rumen and proximal duodenum were used in a 4×4 Latin square experiment to evaluate the influence of supplemental dry distillers grain with solubles (DDGS) levels (0, 10, 20 and 30%, dry matter basis) in substitution for dry-rolled (DR) corn on characteristics of digestive function and digestible energy (DE) of diet. Treatments did not influence ruminal pH. Substitution of DR corn with DDGS increased ruminal neutral detergent fiber (NDF) digestion (quadratic effect, p&lt;0.01), but decreased ruminal organic matter (OM) digestion (linear effect, p&lt;0.01). Replacing corn with DDGS increased (linear, p≤0.02) duodenal flow of lipids, NDF and feed N. But there were no treatment effects on flow to the small intestine of microbial nitrogen (MN) or microbial N efficiency. The estimated UIP value of DDGS was 44%. Postruminal digestion of OM, starch, lipids and nitrogen (N) were not affected by treatments. Total tract digestion of N increased (linear, p = 0.04) as the DDGS level increased, but DDGS substitution tended to decrease total tract digestion of OM (p = 0.06) and digestion of gross energy (p = 0.08). However, it did not affect the dietary digestible energy (DE, MJ/kg), reflecting the greater gross energy content of DDGS versus DR corn in the replacements. The comparative DE value of DDGS may be considered similar to the DE value of the DR corn it replaced up to 30% in the finishing diets fed to lambs

Fatty acid bioaccessibility and structural breakdown from in vitro digestion of almond particles.

Previous studies have shown that the size of almond particles influences lipid bioaccessibility during digestion. However, the extent of structural breakdown of almond particles during gastric digestion and its impact on lipid bioaccessibility is unclear. In this study, in vitro digestion of almond particles was conducted using a dynamic model (Human Gastric Simulator) and a static model (shaking water bath). Structural breakdown of particles during the gastric phase occurred only in the Human Gastric Simulator, as evidenced by a reduction in particle size (15.89 ± 0.68 mm2 to 12.19 ± 1.29 mm2, p &lt; 0.05). Fatty acid bioaccessibility at the end of the gastric phase was greater in the Human Gastric Simulator than in the shaking water bath (6.55 ± 0.85% vs. 4.54 ± 0.36%, p &lt; 0.01). Results showed that the in vitro model of digestion which included peristaltic contractions (Human Gastric Simulator) led to breakdown of almond particles during gastric digestion which increased fatty acid bioaccessibility

Improving Biomethanation of Chicken Manure by Co-Digestion with Ethanol Plant Effluent

As the global production of chicken manure has steadily increased, its proper management has become a challenging issue. This study examined process effluent from a bioethanol plant as a co-substrate for efficient anaerobic digestion of chicken manure. An anaerobic continuous reactor was operated in mono- and co-digestion modes by adding increasing amounts of the ethanol plant effluent (0%, 10%, and 20% (v/v) of chicken manure). Methanogenic performance improved significantly in terms of both methane production rate and yield (by up to 66% and 36%, respectively), with an increase in organic loading rate over the experimental phases. Correspondingly, the specific methanogenic activity was significantly higher in the co-digestion sludge than in the mono-digestion sludge. The reactor did not suffer any apparent process imbalance, ammonia inhibition, or nutrient limitation throughout the experiment, with the removal of volatile solids being stably maintained (56.3???58.9%). The amount of ethanol plant effluent appears to directly affect the rate of acidification, and its addition at ???20% (v/v) to chicken manure needs to be avoided to maintain a stable pH. The overall results suggest that anerobic co-digestion with ethanol plant effluent may provide a practical means for the stable treatment and valorization of chicken manure

Bio-Fertilizers via Co-Digestion: a Review

In diversifying the economies of most oil producing countries especially in regions with arable lands, Agriculture becomes the next choice aside mineral deposits. This has led to a search for an alternative to inorganic fertilizers, the alternatives are the biofertilizers. The paper discussed the classification of the anaerobic co-digestion process based on the application of inoculants to the biodigester feedstock to speed up the digestion process and the absence of inoculants. Biodigester feedstock also looked at the various mechanisms in the digestion process which includes hydrolysis, acidogenesis, acetogenesis, and methanogenesis, the pathways were illustrated with chemical equations and various microorganisms that take part in the anaerobic process were mentioned and tabulated. The types of biofertilizers, merits, and demerits, the difference between biofertilizers and organic fertilizers were comprehensively discussed. Current trends on the application of the co-digestion technique to improve the yield, nutrient, and safety of biofertilizers and also the recent progression on the technique were mentioned

Two phase continuous digestion of solid manure on-farm: design, mass and nutrient balance

During the last decade some so called ‘dry fermentation’ prototype plants were developed for anaerobic digestion of organic material containing 15-50 % total solids. These plants show added advantages com-pared to slurry digestion plants: Less reactor volume, less process energy, less transport capacity, less odour emissions. However on-farm dry fermentation plants are not common and rarely commercially available. This paper reports about an innovative two phase prototype biogas plant designed for continuous digestion of solid dairy cattle manure

Dry anaerobic digestion of organic residues on-farm - a feasibility study

Objectives The feasibility study shall answer the following questions: Are there economical and ecological advantages of on-farm dry digestion biogas plants? How the construction and operation parameters of a dry digestion biogas plant influence environment, profit, and sustainability of on-farm biogas production? The aim of the feasibility study is to provide facts and figures for decision makers in Finland to support the development of the economically and environmentally most promising biogas technology on-farm. The results may encourage on-farm biogas plant manufacturers to develop and market dry anaerobic digestion technology as a complementary technology. This technology may be a competitive alternative for farms using a dry manure chain or even for stockless farms. Results Up to now farm scale dry digestion technology does not offer competitive advantages in biogas production compared to slurry based technology as far as only energy production is concerned. However, the results give an over-view of existing technical solutions of farm-scale dry digestion plants. The results also show that the ideal technical solution is not invented yet. This may be a challenge for farmers and entrepreneurs interested in planning and developing future dry digestion biogas plants on-farm. Development of new dry digestion prototype plants requires appropriate compensation for environmental benefits like closed energy and nutrient circles to improve the economy of biogas production. The prototype in Järna meets the objectives of the project since beside energy a new compost product from the solid fraction was generated. On the other hand the two-phase process consumes much energy and the investment costs are high (>2000 € m-3 reactor volume). Dry digestion on-farm offers the following advantages: Good process stability and reliability, no problems like foam or sedimentation, cheap modules for batch reactors, less reactor capacity, reduced transport costs due to reduced mass transfer in respect of the produced biogas quantity per mass unit, compost of solid digestion residues suitable as fertiliser also outside the farm gate, use of on-farm available technology for filling and discharging the reactor, less process energy for heating because of reduced reactor size, no process energy for stirring, reduced odour emissions, reduced nutrient run off during storage and distribution of residues because there is no liquid mass transfer, suitable for farms using deep litter systems. These advantages are compensated by following constraints: Up to 50% of digestion residues are needed as inoculation material (cattle manure does not need inoculation) requiring more reactor capacity and mixing facilities. Retention time of dry digestion is up to three times longer compared to wet digestion requiring more reactor capacity and more process energy, filling and discharging batch reactors is time and energy consuming. We conclude that only farm specific conditions may be in favour for dry digestion technology. Generally, four factors decide about the economy of biogas production on-farm: Income from waste disposal services, compensation for reduction of greenhouse gas emission, compensation for energy production and - most important for sustainable agriculture - nutrient recycling benefits. Evaluation of the results We did not find any refereed scientific paper that includes a documentation of an on-farm dry digestion biogas plant. It seems that we tried first. We also could not find any results about the biogas potential of oat husks, so we may have found these results first. Farm scale production of anaerobically treated solid manure for composting is new. Dry fermentation biogas plants offer the possibility to design solid manure compost by variation of fermentation process parameters. From different scientific publication databases we found about 10 000 references concerning biogas research during the past 10 years. Less than ten are dealing with biogas reactors for non-liquid substrates on-farm. Recent research mainly concentrates on basic research, biogas process research for communal waste, large-scale biogas plants, and research on laboratory level. This mirrors the fact, that production of research papers is rather financed than product development on site. Our conclusion is that it seems worldwide to be very difficult or even impossible to find financial support for on site research, especially for on-farm prototype biogas reactors. We suppose the following reasons for this fact: biogas plant research requires proficiency in many different scientific disciplines, lack of co-operation between engineering and life sciences, high development costs to transfer basic research results into practical technical solutions, low interest of researchers because on site and on-farm research enjoys low appreciation in terms of scientific credits, portability of farm specific design and process solutions is difficult. Our conclusion is that on site and on-farm research has to be supported by funding agencies if integration of biogas and bio energy into the farm organism is considered as an important target within the agricultural policy framework. Future research on both dry fermentation technique and biogas yield of solid organic residues may close present knowledge gaps. Prototype research may offer competitive alternatives to wet fermentation for farms using a solid manure chain and/or energy crops for biogas production. To encourage farmers and entrepreneurs to foster the development of dry fermentation technology support in terms of education and advisory services is also necessary

Carbon and Energy Life-Cycle Assessment for Five Agricultural Anaerobic Digesters in Massachusetts on Small Dairy Farms

anaerobic digestion, co-digestion, dairy operations, food processing, greenhouse gas emissions, net energy gain, Farm Management, Livestock Production/Industries,

Studi Pengaruh Metode L-AD dan SS-AD terhadap Produksi Biogas dari Limbah Sekam Padi

Abstrak – Proses biogas anaerobic digestion berdasarkan total padatannya terbagi menjadi 2 yaitu Liquid Anaerobic Digestion (L-AD) umumnya terjadi pada kondisi dengan konsentrasi solid antara 0,5% dan 15%. Sebaliknya, Solid State Anaerobic Digestion (SS-AD) terjadi pada konsentrasi padat lebih tinggi dari 15%. Penelitian ini bertujuan untuk mengetahui pengaruh produksi yield biogas dari limbah sekam padi dalam kondisi L-AD dan SS-AD. Variabel yang diamati dalam pengamatan yaitu yield biogas kumulatif. Skala laboratorium dari pencernaan anaerobik digunakan dalam penelitian ini dan dioperasikan dalam sistem batch pada suhu kamar. Rasio C/N yang ditetapkan sebesar 25oC. Jumlah total padatan (TS) bervariasi dari 5, 7, 9% untuk kondisi L-AD dan 19, 21, 23% untuk kondisi SS-AD. Karena kandungan lignin yang tinggi pada sekam padi maka dilakukan perlakuan pendahuluan kimia menggunakan natrium hidroksida (NaOH) untuk memecah struktur lignoselulosanya. Kemudian biogas yang dihasilkan diukur dengan menggunakan metode perpindahan air setiap dua hari selama 60 hari. Hasil penelitian menunjukkan pretreatment natrium hidroksida dapat meningkatkan produksi biogas baik pada kondisi L-AD maupun SS-AD. Didapatkan volume produktivitas tertinggi untuk sekam padi pada kondisi L-AD dengan rasio TS 7% dan pada kondisi SS-AD dengan rasio TS 19% masing-masing sebesar 793 dan 935,5 ml. Produksi biogas spesifik pada TS dari 5, 7, 9, 19, 21 dan 23% adalah 57; 56.64; 45.36; 24.62; 15.15; dan 12.45 ml/gr TS. Untuk hasil yield biogas kumulatif tertinggi didapatkan pada SS-AD dengan rasio TS 19% sedangkan kandungan TS lebih tinggi pada L-AD dengan rasio TS 7%. Hal tersebut karena kandungan TS yang lebih tinggi memilki efek minimal pada efisiensi TS dan penurunan dalam produksi biogas, sehingga kondisi L-AD lebih menguntungkan. Kata Kunci: Biogas, Sekam Padi, Konsentrasi Total Padatan (TS), Liquid Anaerobic Digestion (L-AD), Solid State Anaerobic Digestion (SS-AD) Abstract – The process of biogas anaerobic digestion based on its total solid is divided into 2 ie Liquid Anaerobic Digestion (L-AD) generally occurs in conditions with solid concentration between 0.5% and 15%. In contrast, Solid State Anaerobic Digestion (SS-AD) occurs at a solid concentration higher than 15%. This study aims to determine the effect of production of biogas yield from rice husk waste in the conditions of L-AD and SS-AD. The variables observed in the observation were cumulative biogas yield. The laboratory scale of anaerobic digestion was used in this study and operated in a batch system at room temperature. Estimated C / N ratio of 25oC. The total amount of solids (TS) varies from 5, 7, 9% for L-AD conditions and 19, 21, 23% for SS-AD conditions. Because of the high lignin content in rice husks, a chemical preliminary treatment using sodium hydroxide (NaOH) is used to break the lignocellulosic structure. Then the resulting biogas was measured using the method of water movement every two days for 60 days. The results showed that sodium hydroxide pretreatment can increase biogas production in both L-AD and SS-AD conditions. The highest productivity volume for rice husk was found in L-AD condition with TS ratio of 7% and SS-AD condition with TS 19% ratio of 793 and 935.5 ml, respectively. Specific biogas production on TS of 5, 7, 9, 19, 21 and 23% was 57; 56.64; 45.36; 24.62; 15.15; and 12.45 ml / g TS. The highest cumulative biogas yield was obtained in SS-AD with TS ratio of 19% while TS content was higher in L-AD with TS ratio of 7%. This is because the higher TS content has a minimal effect on TS efficiency and a decrease in biogas production, so the L-AD condition is more favorable. Keywords: Biogas, Rice husk, Concentration of Total Solids (TS), Liquid Anaerobic Digestion (L-AD), Solid State Anaerobic Digestion (SS-AD