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

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

Nutrient balance of a two-phase solid manure biogas plant

So called "dry fermentation" prototype plants for anaerobic digestion of organic material containing 15-50 % total solids show added advantages compared to slurry digestion plants (Hoffman 2001): 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. Recent on-farm research (Kusch & Oechsner 2004) and prototype research (Linke 2004) show promising technical solutions for dry fermentation batch reactors on-farm. The Biodynamic Research Institute in Järna developed a two-phase on-farm biogas plant. The plant digests manure of dairy cattle and organic residues originating from the farm and the surrounding food processing units containing 17.7-19.6 % total solids. A new technology for continuously filling and discharging the hydrolysis reactor was developed and implemented. The output of the hydrolysis reactor is separated into a solid and liquid fraction. The solid fraction is composted. The liquid fraction is further digested in a methane reactor and the effluent used as liquid fertiliser. Initial results show that anaerobic digestion followed by aerobic composting of the solid fraction improves the nutrient balance of the farm compared to mere aerobic composting. Composted solid fraction and effluent together contain about 70 % of total input nitrogen and 94 % of input NH4. The manure that was merely aerobic digested contained about 51 % of total input nitrogen and 3.9 % of input NH4. Additionally anaerobic digestion improves the energy balance of the farm producing up to 269 l biogas kg-1 volatile solids or 1,7 kWh heat kg-1 volatile solids

Microclimate and gas emissions in dairy buildings : Instrumentation, theory and measurements

The aim of this thesis was to develop measurement techniques and systems for measuring air quality and to provide information about air quality conditions and the amount of gaseous emissions from semi-insulated and uninsulated dairy buildings in Finland and Estonia. Specialization and intensification in livestock farming, such as in dairy production, is usually accompanied by an increase in concentrated environmental emissions. In addition to high moisture, the presence of dust and corrosive gases, and widely varying gas concentrations in dairy buildings, Finland and Estonia experience winter temperatures reaching below -40 ºC and summer temperatures above +30 ºC. The adaptation of new technologies for long-term air quality monitoring and measurement remains relatively uncommon in dairy buildings because the construction and maintenance of accurate monitoring systems for long-term use are too expensive for the average dairy farmer to afford. Though the documentation of accurate air quality measurement systems intended mainly for research purposes have been made in the past, standardised methods and the documentation of affordable systems and simple methods for performing air quality and emissions measurements in dairy buildings are unavailable. In this study, we built three measurement systems: 1) a Stationary system with integrated affordable sensors for on-site measurements, 2) a Wireless system with affordable sensors for off-site measurements, and 3) a Mobile system consisting of expensive and accurate sensors for measuring air quality. In addition to assessing existing methods, we developed simplified methods for measuring ventilation and emission rates in dairy buildings. The three measurement systems were successfully used to measure air quality in uninsulated, semi-insulated, and fully-insulated dairy buildings between the years 2005 and 2007. When carefully calibrated, the affordable sensors in the systems gave reasonably accurate readings. The spatial air quality survey showed high variation in microclimate conditions in the dairy buildings measured. The average indoor air concentration for carbon dioxide was 950 ppm, for ammonia 5 ppm, for methane 48 ppm, for relative humidity 70%, and for inside air velocity 0.2 m/s. The average winter and summer indoor temperatures during the measurement period were -7º C and +24 ºC for the uninsulated, +3 ºC and +20 ºC for the semi-insulated and +10 ºC and +25 ºC for the fully-insulated dairy buildings. The measurement results showed that the uninsulated dairy buildings had lower indoor gas concentrations and emissions compared to fully insulated buildings. Although occasionally exceeded, the ventilation rates and average indoor air quality in the dairy buildings were largely within recommended limits. We assessed the traditional heat balance, moisture balance, carbon dioxide balance and direct airflow methods for estimating ventilation rates. The direct velocity measurement for the estimation of ventilation rate proved to be impractical for naturally ventilated buildings. Two methods were developed for estimating ventilation rates. The first method is applicable in buildings in which the ventilation can be stopped or completely closed. The second method is useful in naturally ventilated buildings with large openings and high ventilation rates where spatial gas concentrations are heterogeneously distributed. The two traditional methods (carbon dioxide and methane balances), and two newly developed methods (theoretical modelling using Fick s law and boundary layer theory, and the recirculation flux-chamber technique) were used to estimate ammonia emissions from the dairy buildings. Using the traditional carbon dioxide balance method, ammonia emissions per cow from the dairy buildings ranged from 7 g day-1 to 35 g day-1, and methane emissions per cow ranged from 96 g day-1 to 348 g day-1. The developed methods proved to be as equally accurate as the traditional methods. Variation between the mean emissions estimated with the traditional and the developed methods was less than 20%. The developed modelling procedure provided sound framework for examining the impact of production systems on ammonia emissions in dairy buildings.Erikoistuminen tiettyyn maatalouden osa-alueeseen, kuten maidontuotantoon, aiheuttaa ympäristöpäästöjen kasaantumista. Navetoissa on pölyä, kosteutta ja kaasuja, jotka voivat vaikuttaa lehmien ja työntekijöiden hyvinvointiin sekä heikentää navetan rakenteita. Suuret vuotuiset lämpötilavaihtelut Suomessa ja Virossa (-40 ºC - + 30 ºC) vaikeuttavat lisäksi navetan olosuhteiden mittausta ja seurantaa. Yleensä navetan olosuhteiden mittauslaitteet ovat liian kalliita tavallisille maanviljelijöille. Mittauslaitteita tai -menetelmiä ei ole myöskään standardisoitu, siksi esimerkiksi tulosten vertailu on vaikeaa. Tässä tutkimuksessa käytettiin ja testattiin edullisia mittausantureita ja pyrittiin kehittämään yksinkertaisia mittausmenetelmiä. Tutkimusta varten rakennettiin kolme mittauslaitteistoa 1) Kiinteä laitteisto, johon kytkettiin edullisia antureita paikan päällä tapahtuvaa tiedonkeruuta varten 2) Langaton laitteisto, jossa oli edulliset anturit ja jota pystyttiin seuraamaan etänä matkapuhelinverkkoa hyväksi käyttäen sekä 3) Liikkuva laitteisto, jossa oli perinteisesti käytetyt kalliit ja tarkat mittausanturit. Mittaukset suoritettiin vuosien 2005 2007 aikana kylmäpihatto-, viileäpihatto- ja lämminpihattonavetoissa. Huolellisesti kalibroituna edulliset anturit antoivat kohtalaisen tarkkoja tuloksia. Mittaukset osoittivat, että olosuhteet vaihtelivat suuresti navetan eri osissa. Sisäilman keskimääräinen hiilidioksidipitoisuus oli 950 ppm, ammoniakkipitoisuus 5 ppm ja metaanipitoisuus 48 ppm. Keskimääräinen suhteellinen ilmankosteus oli 70 % ja ilmavirta 0.2 m/s. Keskimääräiset sisäilman lämpötilat oli talvella ja kesällä seuraavat: kylmäpihattonavetoissa -7º C ja +24 ºC, viileäpihattonavetoissa +3 ºC ja +20 ºC sekä lämminpihattonavetoissa +10 ºC ja +25 ºC. Tutkimus osoitti, että kylmäpihattonavettojen päästöt ja sisäilman kaasupitoisuus olivat matalammat kuin lämminpihattonavettojen. Tutkittujen navettojen ilmanvaihto ja sisäilman laatu olivat muutamia poikkeuksia lukuunottamatta vaatimusten mukaisissa rajoissa. Tutkimuksessa testattiin ilmanvaihdon arvioimisessa perinteisesti käytetyt lämpö-, kosteus-, metaani- ja hiilidioksiditaseet, sekä suora ilmanvirtausmittaus. Menetelmät osoittautuivat epäkäytännöllisiksi ja kalliiksi kylmä- ja viileäpihattonavetoissa, joissa ilmanvaihto tapahtuu painovoimaisesti. Arviointitulosten parantamiseksi kehitettiin kaksi uutta mittausmenetelmää. Ensimmäinen sopii tiloihin, joissa ilman virtaus on hyvin voimakasta. Toinen uusista menetelmistä sopii tiloihin, joissa ilmanlaatu vaihtelee rajusti tilan eri osissa. Uudet menetelmät paransivat arviointituloksia. Navetan päästöjä arvioitiin kahden perinteisen menetelmän (hiilidioksidi- ja metaanitase) sekä kahden uuden menetelmän avulla (teoreettinen mallintaminen sekä virtauskammio). Ammoniakkipäästöt lehmää kohti vaihtelivat 7 grammasta 35 grammaan päivässä, metaanipäästöt vaihtelivat vastaavasti 96 ja 348 gramman välillä. Uudet mittausmenetelmät olivat helppokäyttöisempiä, mutta tarkkuudeltaan perinteisten menetelmien veroisia. Mallintamismenetelmä osoitti tärkeät ammoniakkipäästöihin vaikuttavat tekijät lypsykarjatuotannossa

Microbial quality of chevon and mutton sold in Tamale Metropolis of Northern Ghana

The microbial quality of 80 meat samples made up of 40 chevon and 40 mutton were collected from the Aboabo, Central-internal, Central-external, and Sakasaka meat shops in Tamale Metropolis and assessed in order to ascertain it  safety. Chevon from Aboabo and mutton from the Central market-internal had the highest mean total aerobic bacterial count of 3.9 X 10 6 cfu/cm2 and 3.7 X 106 cfu/cm2 , respectively. The lowest total aerobic count in chevon was found in the Central-internal (6.0 X 105 cfu/cm2) and that of mutton was  found in Sakasaka market meat shop (6.0 X 10 5 cfu/cm2). Bacteria isolated from the samples were  Escherichia coli, Streptococcus species, Salmonella species , Enterococcus species, and Staphylococcus species, some of which harbor human pathogens of public health concern. The isolation of various bacteria in chevon and mutton sold in the Tamale Metropolis indicates that, lower standard  of operating systems in the slaughtering, processing and sale of meats are adhered to. The Government of Ghana, Ministry of Health and Ministry of Food and Agriculture should enforce the laws that prohibit the illegal slaughtering of animals without veterinary inspection, unstandardized methods of handling animals, slaughtering and selling of meats on the open market. @JASEMJ. Appl. Sci. Environ. Manage. December, 2010, Vol. 14 (4) 53 - 5

Biogas aus Festmist – eine neue Technologie zu Schließung des Nährstoff- und Energiekreislaufes auf dem landwirtschaftlichen Betrieb

The Biodynamic Research Institute in Järna developed at the farm Yttereneby a two phase biogas plant. The plant digests manure of dairy cattle and organic residues originating from the farm and the surrounding food processing units containing 17,7 - 19,6 % dry matter. A new technology for continuously filling and discharging the biogas reactor was developed and implemented. Digestion residues are separated into a solid fraction for composting and into a liquid fraction. The solid fraction is suitable for aerobic composting. Initial results show that anaerobic digestion and following aerobic composting of the solid fraction improves the nitrogen balance of the farm compared to mere aerobic composting. Composted biogas plant residues and effluent together contain 70,8 % of input Ntot and 93,3 % of input NH4, merely aerobic digested manure 51,3 % Ntot and 3,9 % NH4 only. Additionally anaerobic digestion improves the energy balance of the farm producing up to 269 l biogas kg-1 VS or 1,7 kWh heat kg-1 VS

Nutrient balance of a two-phase solid manure biogas plant

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Kuivalannan kaksivaiheinen jatkuvatoiminen mädätys maatilalla: Reaktorin rakenne sekä aine-, ravinne- ja energiataseet

Viime vuosikymmeninä on maatiloille kehitetty muutamia kuivamädätyslaitosten prototyyppejä. Kuivamädätyslaitosten etuja, verrattuna lietteiden mädätyslaitoksiin, ovat pienempi reaktorin koko, prosessienergian kulutus ja kuljetustarve sekä pienemmät hajukaasupäästöt. Kuivamädätyslaitokset eivät kuitenkaan ole yleistyneet maatiloilla, koska reaktorin syöttö- ja tyhjennysvaiheet ovat olleet hankalia toteuttaa. Tässä esitetään uudenlainen kaksivaiheinen tilatason biokaasulaitos, joka on jatkuvatoiminen ja jolla mädätetään lypsykarjan kuivalantaa. Lypsykarjatilalta tuleva kuivalanta siirretään hydraulisella raapalla hydrolyysireaktorin syöttökanavaan, josta se puristetaan hydrolyysireaktorin yläosaan. Reaktori on vinossa, 30° kulmassa, ja sen tehollinen tilavuus on 53 m3. Tuore materiaali sekoittuu muuhun materiaaliin painovoiman avuilla. Viipymäaika on 22 - 25 päivää 38 °C:ssa, minkä jälkeen materiaali poistetaan reaktorin alaosasta laatikon avulla. Osa materiaalista putoaa kuljetusruuvin alapuolella olevaan puristimeen, missä erotetaan toisistaan kiinteä ja nestemäinen jae. Toinen osa johdetaan takaisin syöttökanavaan ja syötetään tuoreen lannan sekaan. Kiinteä jae, joka saadaan puristimesta, kompostoidaan lantalassa. Nestemäinen jae kerätään ja pumpataan metaanireaktoriin, jonka tehollinen tilavuus on 17 m3. Nestemäinen jae, altaasta ja metaanireaktorista, palautetaan osittain syöttöputkeen, tukkeutumisen estämiseksi. Mädätetty neste pumpataan 15 - 16 päivän hydraulisen viipymäajan jälkeen varastosäiliöön. Vertailukokeessa kompostoitiin rinnakkain käsittelemätöntä lantaa sekä hydrolyysireaktorista tulevaa kiinteää jaetta.Biokaasulaitos tuotti kaasua keskimäärin 52 m3 vuorokaudessa, suurin mitattu saanto vuorokaudessa oli 91 m3 biokaasua tai metaanin määränä ilmaistuna 0,17 m3 CH4 orgaanista kuiva-ainekiloa kohti. Kiinteä jae sisälsi 73 ± 2 % syötetystä orgaanisesta kuiva-aineesta ja nestemäinen mädätysjäännös 10 ± 2 %. Kompostoitu kiinteä jae ja nestemäinen mädätysjäännös sisälsivät yhteensä 70 – 81 % kuivalannan kokonaistyppimäärästä ja 94 – 111 % kuivalannan ammoniumista. Kokonaistyyppihäviö oli 19 - 29 %. Lannan kompostoinnissa ammoniumhäviö oli 96 % ja kokonaistyyppihäviö 30 – 48 %. Tuotetusta metaanista kului keskimäärin 76,3 % prosessin lämmittämiseen ja enimmillään 56 % tuotetusta energiasta (305 kWh d-1) oli käytettävissä maatilan lämmitykseen. Kaksivaiheinen biokaasureaktorin prototyyppi on toimiva ratkaisu Ytterenebyn maatilan ja läheisen elintarvikeyrityksen orgaanisen jätteen käsittelyyn. Biokaasulaitoksen rakenteessa on otettu huomioon uusimmat tutkimustulokset. Prosessioptimoinnin jälkeen taloudellinen arviointi on tarpeellista arvioitaessa uuden tekniikan kilpailukykyä

Not All Street Food Is Bad: Low Prevalence of Antibiotic-Resistant Salmonella enterica in Ready-to-Eat (RTE) Meats in Ghana Is Associated with Good Vendors’ Knowledge of Meat Safety

Foodborne infections due to the consumption of meat is a significant threat to public health. However, good vendor and consumer knowledge of meat safety could prevent meat contamination with and transmission of foodborne pathogens like Salmonella. Thus, this study investigated the vendor and consumer perception, knowledge, and practices of meat safety regarding ready-to-eat (RTE) meat and how this affected the prevalence and antibiotic susceptibility of Salmonella enterica in RTE meats in the streets of Ghana. A semi-structured questionnaire was used to obtain the demographics, knowledge, and practices of meat safety data from RTE meat vendors (n = 300) and consumers (n = 382). Salmonella enterica detection was done according to the United State of America (USA)-Food and Drugs Administration (FDA) Bacteriological Analytical Manual. The disk diffusion method was used for antibiotic resistance testing. The results revealed that most of the respondents had heard of meat safety (98.3% vendors, 91.8% consumers) and knew that meat could be contaminated by poor handling (100.0% vendors, 88.9% consumers). The respondents knew that regular hand washing reduced the risk of meat contamination (100.0% vendors, 94.0% consumers). Responses to the practices of meat safety by vendors were generally better. A very low Salmonella enterica prevalence was observed in the samples, ranging between 0.0 and 4.0% for guinea fowl and beef, respectively. However, the six isolates obtained were resistant to five of the nine antibiotics tested, with all isolates displaying different resistance profiles. Overall, the good knowledge and practice of meat safety demonstrated by the respondents corroborated the negligible prevalence of Salmonella in this study, reiterating the importance of vendor meat safety knowledge. However, the presence of resistant Salmonella enterica in some of the meat samples, albeit in a very low prevalence, warrants stricter sanitary measures and greater meat safety awareness in the general population to prevent meat-borne infections and potential transmission of drug-resistant bacteria to humans

Parenting practices and family relationships during the COVID-19 lockdown in Ghana

The effects of the COVID-19 pandemic have been far reaching across almost every sphere of life. Families, which are the basic units of society, have not been spared the ravages of the pandemic. Changes in family daily routines as a result of COVID-19 can affect spousal relationships, parenting and childcare practices. However, the extent to which the pandemic has affected parenting practices and family relationships in Ghana is not known. The goal of this study was to assess how parenting practices and family relationships have been influenced during the COVID-19 pandemic in Ghana. Data for this paper was drawn from an online questionnaire response from 463 participants in Ghana as a subset analysis from a multi-country study on personal and family coping system with COVID-19 pandemic in the global south. The mean score for pre-COVID-19 relationship with partner (36.86) was higher (p<0.0001) than the mean score for during COVID-19 relationship with partner (35.32) indicating that COVID-19 has had negative influence on relationships. The mean score for pre-COVID-19 parenting (32.78) was higher (p<0.0001) compared to the mean score for during COVID-19 parenting (31.40) indicating negative influence on parenting. We have predicted that participants whose coping levels were “Well” on the average, are likely to be doing well in relationship with partners and parenting practices during the COVID-19 period The challenging public health containment measures of the COVID-19 pandemic have negatively influenced the relationship between partners and parenting practices in Ghana