Two different organic waste management systems have been studied in the BERAS project. The most extensive study was of biowaste and nutrient flows in the community of Juva, Finland. The research methods used were waste flow and substance flow studies

Lehto, Tiina

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Organic Eprints

E K O L O G I S K T   L A N T B R U K   N R   4 6   •  D E C E M B E R   2 0 0 5ENVIRONMENTALIMPACTS OF ECO-LOCAL FOOD SYSTEMS– final report fromBERAS Work Package 2Artur Granstedt, Olof Thomssonand Thomas Schneider (eds.)Centrum för uthålligt lantbrukBaltic Ecological Recycling Agriculture and Society (BERAS) Nr. 598     E K O L O G I S K T   L A N T B R U K   N R   4 6   •   D E C E M B E R   2 0 0 5C H A P T E R   VIIORGANIC WASTEMANAGEMENT STUDIESTwo different organic waste management systems have been studiedin the BERAS project. The most extensive study was of biowaste andnutrient flows in the community of Juva, Finland. In Järna, Sweden, afarm-size biogas plant was studied. Based upon the results of thesestudies a discussion about the possibilities for combined recycling (re-use of nutrients and humus) and energy ‘production’ is presented.Inventory in JuvaThe objective of the inventory conducted in Juva was to determine thepossibilities for recycling the biowaste (organic waste) produced by localfood actors back into agriculture production. The food actors in thestudy included: food processors, grocery stores, schools, communalkitchens, and private consumers, i.e. all the actors in the food chainexcept the primary producers, farmers. The research methods used werewaste flow and substance flow studies.The study first looked into the current waste management systemwithin the Juva community and among specific food actors. Specialattention was paid to biowaste and nutrient flows. Because biowasterecycling into agricultural fields in Juva was uncommon in 2002, anassessment was made of the possibilities to recycle biowaste back intoagriculture.Recycling of biowaste can put humus and nutrients back intoagriculture land. In organic agriculture, nitrogen is fixated by plantsbut a lack of phosphorus is predicted in the future. Biowaste couldcomplement nitrogen fixation and it could also be a good source ofphosphorus. Legislation in Finland restricts the use of biowaste andsewage sludge. For example, neither may be used in organic agriculture.Regulation (EC) No. 1774/2002 was enacted mainly because of the BSCand foot and mouth disease epidemic and lays down health rulesconcerning animal by-products not intended for human consumption.It restricts the recycling of animal-based by-products, including foodwaste from kitchens and animal-based biowaste from grocery stores.Materials and methodsThe system under study includes food actors in the Juva populationcentre: a few food processors in the urban area processing meat, milk,vegetables and cereals; three communal kitchens including schools;three grocery stores and private households. The wastewater enteringthe communal wastewater treatment plant and the sewage sludge for-med there were also studied. The research methods used were wasteflow and substance flow studies. The substance flow study lookedspecifically at nitrogen (N) and phosphorous (P) in the biowaste.Data for the study was mainly obtained through informalTiina Lehto, South Savo RegionalEnvironment Centre, Finland99C H A P T E R   VIIinterviews, enquiries and analyses results (Savolab Oy 2003, Jyväskylänyliopisto, 2005). An assessment of the amount of biowaste produced byhouseholds was made. This was necessary because an unknown partof the household biowaste ends up as landfill waste. The estimatedamount of biowaste produced by households has been calculated basedon the following assumptions:• Juva had a population of 7449 in 2002, and 3628 (48.7 %) live withinthe population centre and 3821 (51.3 %) live in the surroundingcountryside.• The average per capita annual waste production in the region is about220 kg (Angervuori 2002);• About 33 % of all household waste in population centres and about40 % of the household waste produced in rural areas is biowaste(Statistics Finland 1994);• In the case of the Juva population centre, about 40 % of the inhabitantsare included in separate biowaste collection and about 70 % of theirtotal biowaste is collected. (Rejlers Oy 2000)• The remaining 60 % in the Juva population centre compost theirbiowaste on their property (YTI-tutkimuskeskus, 2004);• The inhabitants of the rural area of Juva are obligated to composttheir biowaste.The nutrient values used for different foodstuffs and biowastes Table7-1) are based on the Fineli-Finnish Food Consumption Database of theNational Public Health Institute (National Public Health Institute, 2005).The dry matter content has been estimated based on the feed tablesproduced by Agronet (2005). Separately collected biowaste is assumedto contain 20 g N and 4 g P per kg dry matter (dm). The dry mattercontent is assumed to 35 mass-percent (Sokka et al. 2004).Table 7-2 shows the estimates of the nutrients included inhousehold wastewater based on the estimates presented by Eilersen etal. (Magid et al. 2002) and data for the incoming and outgoingwastewater at the sewage treatment plant obtained from Savolab Oy(2003). The latter data are based on the average daily nutrient concent-ration of five samples analysed in laboratory conditions. The conversionfactor used for biowaste is 0.3 tonnes/m3.Laboratory analyses of sewage sludge samples from the Juvawastewater treatment plant and from compost samples from the Juvastack-composting area (Jyväskylän yliopisto, 2005) to determine totalnutrients available for recycling at present and whether the heavy metalconcentrations are below the regulated limits were made in the study.Results – the waste system in JuvaFigure 7-1 shows the biowaste flows produced by the various food actorsin 2002 and Figure 7-2 presents an assessment of the nutrient flowsincluded in biowaste. The total amount of solid biowaste produced bythe various food actors was about 1150 tonnes. This contained 27.6100     E K O L O G I S K T   L A N T B R U K   N R   4 6   •   D E C E M B E R   2 0 0 5C H A P T E R   VIItonnes of N and 1.6 tonnes of P (excluding poultry waste). About 214tonnes were treated in the communal waste management system bystack-composting the waste. The biowaste in the stack-compost con-tained about 0.71 tonnes of N and 0.15 tonnes of P. The stack-compostedbiowaste originated mainly from households (45 t) and from onevegetable processor (150 t); the remainder came from grocery stores (12t) in the population centre and from communal kitchens (7 t). About10% of the biowaste originating from grocery stores was estimated tobe former animal-based foodstuffs. A maximum of 12 % of the biowastewas treated in the food actors’ own small-scale composting systemsbut little appears to have been utilised on fields to benefit foodproduction. About 70 % of the biowaste produced was transportedoutside Juva; a large amount going to the animal fodder industry. Thiscontained as much as 89 % (24.6 t) of the nitrogen and 66 % (1.05 t) ofthe phosphorous in the biowaste produced by the food actors coveredby this study. A smaller amount appears to have ended up in a landfillin Mikkeli (50 km away) along with mixed waste.Wastewater led to the Juva wastewater treatment plant is mainlyfrom households. The major industrial plants in the area are a dairyand a slaughterhouse, adding BOD (biological oxygen demandingsubstances) and nutrients to the incoming wastewater. In addition wastewater from a vegetable processor, a printing house and a fur refineryare led to the waste water treatment plant. The wastewater treatmentplant in Juva is a BIOLAK treatment plant built in 1982. More recentlya facility for phosphorus precipitation by iron(II)sulphate has beenadded on. The resulting sewage sludge is subjected to filter-pressing;with polymers being used as aiding agents. In 2002, the incomingwastewater to the treatment plant amounted to 421000 m3. This had asolid matter content of 134 tonnes and contained 22.0 tonnes of N and4.7 tonnes of P. The amount of iron(II)sulphate used was 80.7 tonnesTable 7-1. The nutrient values used for different kinds of foodstuffs andbiowaste.Waste component N P Dry matterLettuce (g/kg) 1.76 0.4 10.3 %1Oat husk (g/kg) 282 4.3 2 88 %Turkey offal (g/kg) 35.2 1.5 35 %Raw milk (g/kg) (Tuhkanen 2005) 5.2 1 12 %Organic milk (g/kg) 4.8 0.9 12 %Pig carcass (g/kg) 27.5 1.8 35 %Separately collected biowaste (g/kg dry matter) 20 4 35 %Household wastewater 14 2.2 135- faeces g/cap/day 1 0.5 35- urine g/cap /d 11 1.5 60- kitchen liquid waste g/cap/d 0.5 0.1 20- bathroom, grey water g/cap/d 1 0.3 20Nutrients to treatment plant, kg/d (Savolab Oy 2003) 60.4 12.8Nutrients into water systems, kg/d (Savolab Oy 2003) 49.2 0.461 Dry matter of cabbage.2 Nutrients in oat bran.101C H A P T E R   VII(Savolab Oy 2003) and the removal efficiency of phosphorous was 96 %and that of nitrogen 19 %.The amount of sewage sludge formed in 2002 was 512 m3 (about395 tonnes1) with a dry matter content of 18 % (wet base). According tothe 2005 analyses results (\h Table 7-3), the sewage sludge dry matterwas 4.4 % N and 2.9 % P. Thus, the sewage sludge contains a maximumof 4.1 tonnes of N and 2.7 tonnes of P. Nitrogen can escape from theprocess through denitrification and evaporation, but phosphorus isbelieved to be slightly soluble because of phosphorus precipitation. Theheavy metal concentrations of the sewage sludge are below the regulatedlevel for agricultural use with exception of chromium. The chromiumconcentration was much higher than the permitted amount.The sewage sludge formed was composted in the communal stack-composting area along with the separately collected biowaste. Tree bark,leaves and gravel were mixed in with the sludge and biowaste topromote the composting process and to produce a final product of bet-ter quality. The nutrient concentrations of the compost as analysed in2005 were low; 0.28 % N and 0.32 % P, but the heavy metal concentrationswere well below the required levels. The concentration of nutrients inthe biowaste is assumed to be the same as in 2002, because no note-worthy changes in biowaste flows or treatment have occurred. Accor-ding to a decision of the Ministry of Agriculture and Forestry (46/1994),the humus content of compost has to be at least 20 % of the dry mattercontent. The compost product has previously been used in green areasand in road construction, and now it is being stored for the purpose oflandscaping an old landfill.DiscussionIn 2002, biowaste composted in stacks in Juva could not be recycledback into agriculture. The treatment process did not fulfil the require-ments, especially the by-product directive 1774/2002 as the compostincluded former animal-based by-products in the form of food wasteand former animal-based foodstuffs from grocery stores. The finalproduct could only be used in landfills (as covering or filling material).If the final product is to be used in agriculture or in greening areas inthe future, then the composting treatment has to fulfil the requirementsof the by-product directive. Another alternative is to compost only thebiowaste of vegetables and other non-animal-based by-products andsewage sludge.Alternative treatment processes for recycling biowaste nutrientsand humus are biogas treatment and composting (centralized or small-scale co-digestion treatment plant). The treatment of biowaste andwastewater causes nutrient losses and all nutrients in the treatedbiowaste do not become available to plants. Figure 7-3 shows totalnutrient and dry matter percentages of the biowaste produced by the1 According to analysis made in 2005 volume weight was 771 g/l (Table 7-2).102     E K O L O G I S K T   L A N T B R U K   N R   4 6   •   D E C E M B E R   2 0 0 5C H A P T E R   VIIFigure 7-1. Biowaste flows involving Juva food actors in 2002 (DM = dry matter).Figure 7-2. Nutrient flows of biowaste involving Juva food actors in 2002. 103C H A P T E R   VIITable 7-2. Analyses results for the compost product from the stack-composting area and the sewage sludge from thewastewater treatment plant in Juva (Jyväskylän yliopisto, 2005).Analysed property Unit Sewage sludge Vnp1 282/1994 MMMp2 46/1994 Compostfrom Juva from JuvaVolume weight g/l 771 696Conductivity mS/m 30.6 2.70pH-value pH 6.5 6.6Ignition loss % DM 65 33Dry matter (DM) % 18 74Total nitrogen % DM 4.4 0.28Total phosphorus % DM 2.9 0.32Total potassium % DM 0.20 0.18Total magnesium % DM 0.16 0.21Total calcium % DM 1.1 0.28Mercury mg/kg DM 0.24 1.0 2.0 0.07Cadmium mg/kg DM 0.6 1.5 3.0 < 0.5Total chromium mg/kg DM 530 300 - 21Copper mg/kg DM 240 600 600 39Lead mg/kg DM 31 100 150 6Molybdenum mg/kg DM 3 - - < 1Nickel mg/kg DM 20 100 100 7Sulphur mg/kg DM 6 800 - - 520Zinc mg/kg DM 480 1 500 1 500 88DM = dry matter1 Decision of the Council of State (Vnp) No 282/1994.2 Decision of Ministy of Agriculture and Forestry (MMMp) No 46/1994.different food actors, including wastewater to the treatment plant, inJuva in 2002. Most of the nutrient-containing components originatedfrom food processors and from urine. Slaughterhouse waste and food-processing waste contained 52 % of the N and 19 % of the P of the totalnutrients which is the equivalent of 93 % of the N and 75 % of the P inthe solid biowaste fraction. Urine contained 29 % of N and 32 % of P ofthe total nutrient which is the equivalent of 66 % of the N and 43 % ofthe P in the wastewater fraction. Slaughterhouse waste contains a lot ofnutrients. However the current regulations pertaining to use of ani-mal-based by-products prevent the recycling of these nutrients back toagricultural land.It should be noted that urine contains about 1/3 of the nutrientsformed within the studied food system and even a greater share of thenutrients in incoming wastewater flow to wastewater treatment plantin Juva in 2002. From the environmental viewpoint, separate urine col-lection would be preferable to the conventional system. It would increasethe amounts of recyclable nutrient available for use on fields and at thesame time make possible the decrease of emissions into water systems.In addition, phosphorous would be in a more usable form for plantsand the risk of heavy metals would be minor compared to sewagesludge. However, with present technology separate urine collection isnot acknowledged as an appropriate system in urban areas.104     E K O L O G I S K T   L A N T B R U K   N R   4 6   •   D E C E M B E R   2 0 0 5C H A P T E R   VIIFigure 7-3. N, P and DM flows of biowaste and wastewater to the treatmentplant in 2002, Juva. (Dry matter of wastewater is assumed to be double thatof solid matter content.)

Organic waste management studies : inventory in Juva

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