Composting green waste with other wastes to produce manufactured soil
Oxana Belyaeva and Richard Haynes
School of Land, Crop and Food Sciences/CRC CARE, The University of Queensland, St Lucia, QLD, Australia, Email
o.belyaeva@uq.edu.au and r.haynes1@uq.edu.au
Abstract
Manufactured soil for landscaping purpos was produced by composting for 6 weeks (a) municipal green waste alone, (b) green waste amended with 25% v/v poultry manure or (c) green waste immerd in, and then removed from, a mixture of liquid grea trap waste/ptage. During composting, temperatures reached 52ºC in green waste alone, 61ºC in poultry manure-amended and 78ºC in grea trap/ptage-amended green waste. Following composting, each of the materials was split into (i) 100% compost, (ii) 80% compost plus 20% v/v soil and (iii) 70% compost plus 20% soil plus 10% coal fly ash. Addition of soil, or soil and ash, to composts incread bulk density, reduced total porosity and incread available water holding capacity. Bicarbonate- extractable P, exchangeable
NH4+ and NO3-, EC and basal respiration were all markedly greater in the grea trap/ptage-amended than poultry manure-amended or green waste alone treatments. Values for extractable P and EC were considered large enough to be damaging to plant growth and germination index (GI) of watercress was less than 60% for all grea trap/ptage composts.
Key Words
Green waste, grea trap waste, compost, available water, available nutrients, microbial activity Introduction
Municipal green waste consists of a range of materials including tree wood and bark, prunings from young trees and shrubs, dead and green leaves and grass clippings and it originates from both domestic dwellings and municipal parks, gardens and rerves. In most cities in the developed world, green waste is collected parately from other wastes and is mechanically shredded and then composted, either alone or with other organic wastes. It is ud in products such as garden mulch, organic soil amendment, garden compost and soilless potting media. However, in Australia, the main u for the composted material is as “manufactured soil” ud for field landscaping purpos in place of natural topsoil. Often, inorganic additives (e.g. sand, subsoil, fly ash) are blended with the c
omposted material. Nevertheless, the inorganic component makes up only 10-30% v/v of the final product. The product is considerably cheaper than excavated natural topsoil and is therefore commonly ud by landscape contractors.
The exact nature of the ingredients, other than green waste, the ratios at which they are mixed and length of the composting period have been arrived at by trial and error and differ appreciably between contractors. Whilst the above operations are commonplace in Australia, and may well have more widespread application, to date little scientific evaluation of the operations and the products produced has been performed. Indeed, although green waste is commonly composted (Bradshaw et al., 1996; Manr and Keeling, 1996) and a number of workers have investigated the properties of the composted material (e.g. Zaccheo et al., 2002; Brewer and Sullivan, 2003), there appear to be no reports, other than that of Belyaeva and Haynes (2009), on its u as the basis of the production of manufactured soils. The aim of this study was to compare composting intensity and the properties of manufactured soils produced through composting green waste alone or co-composting it with an easily-decomposable activator material such as poultry manure or grea trap waste/ptage. Following initial compost production, the products were amended with 20% topsoil, or 20% topsoil plus 10% coal fly ash (to produce manufactured soil) and allowed to mature.
Materials and methods
北京出国留学机构
Materials and composting
Municipal green waste was collected from Phoenix Power Recyclers, Yatala, Queensland, soon after it had been mechanically shredded. Recently-deposited fly ash was collected from the fly ash disposal lagoon at Tarong Power Station, 80 km west if Brisbane. Poultry manure was collected from a commercial egg producer. Liquid grea trap waste and ptic tank waste were collected parately and deposited in a aled lagoon at Phoenix Power Recyclers. The A and B horizon of a silt loam soil classified as a Clastic Rudosol (Isbell, 2002) was excavated from an unfertilized area under native vegetation. The compost treatments were, (1) 100% green waste (GW), (2) 75% green waste/25% poultry manure v/v (GWP) and (3) green waste
T e m p e r a t u r e (ºC ) immerd in a liquid mixture of grea trap waste/ptage for 6 hours and then removed (GWG). Two hundred litre samples of the mixtures were placed in 250 litre plastic composting bins. The experiment was replicated 3 times. Piles were turned every 7 days in order to ensure adequate O 2 levels inside piles. Temperature was
rubinamonitored at a depth of 40 cm inside the piles at 0900 h each day. The water content of piles was m
aintained at 60-70% of their water holding capacity. After 6 weeks of composting each treatment replicate was split into 3: (i) 100% compost (Control), (ii) 80% compost plus 20% v/v soil (S) and (iii) 70% compost plus 20% soil and 10% fly ash v/v/v (SA). The resulting materials were thoroughly mixed and allowed to react and mature for a further 4-week period.
GW
GWP GWG我爱你的英文
1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 33 35 37 39 41 Com posting t i m e (day s)woll
Figure 1. Temperature during composting in composts compod of green waste alone (GW), green waste plus poultry manure (GWP) and green waste plus grea trap waste (GWG).
Compost analys
Ten subsamples were taken randomly from within each pile. Subsamples were bulked, homogenid and ground to pass a 5mm sieve. A part of each sample was stored at 4ºC for microbial and physical analysis and the rest was air-dried and stored for chemical analysis. Electrical conductivity and pH w
ere analyd in a 1:5 (v/v) water extract using a glass electrode. Extractable mineral N was extracted with 2 M KCl (1:100 ratio for 1 h) followed by colorimetric analysis of NH 4+ and NO 3--N using a discrete analyr (Cleverchem, Dechem-Tech, Hamburg, Germany). Available P was extracted with 0.5 M NaHCO 3 (pH 8.5) (1:100 w/v for 16 h) (Colwell, 1963) and measured colorimetrically. Bulk density was determined on naturally compacted samples, particle density by the pycnometer method and total porosity by difference. Soil water content in samples was determined at -10 and -1500 kPa using a pressure plate apparatus.
A germination test was carried out (in quadruplet) on filter paper in petri dishes. Two ml of aqueous extract (1/10 w/v) from composts was added to dishes. Ten eds of watercress (Lepidium sativum) were placed on the filter paper and dishes placed in the dark at 28ºC. The germination index percentage with respect to control (distilled water) was determined after 5 days. The control GI value was considered as 100%.
The statistical significance of experimental treatments was determined by Analysis of Variance Analysis using the Minitab Statistical Software Package and differences were calculated at the 5% level using Tukey ’s test.
Results and discussion
The composition of municipal green waste is typically dominated by shredded wood and bark, with high lignin and tannin contents respectively, and the components are not readily decompod by microbial activity (Francou et al ., 2008). In addition, green waste is often left in stockpiles before shredding and/or composting. During the periods, much of the “soft ” green waste decompos thus further contributing to its slow
decomposition during subquent composting. As a result, temperatures during composting of green waste- alone only reached 52ºC for a short period and then declined (Figure 1). In order to initiate a more active pha of inten microbial activity during composting, the addition of a readily decomposable organic material is required. Addition of poultry manure at 25% v/v to green waste was shown here to both prolong the period over which temperatures were elevated as well as rai the temperature attained to 61ºC (Figure 1). The grea trap waste tended to coat the green waste thus offering a large surface area for microbial decomposition during composting (Coker 2006). Lipids are easily degraded under aerobic conditions (Wakelin and Forster 1977) and their high energy content resulted in composting rapidly achieving thermophilic temperatures. Maximum temperature reached was 78ºC (Figure 1).
Table 1. Some physical and chemical properties and germination index in green waste (GW), green
waste plus poultry manure (GWP) and green waste plus grea trap waste/ptage (GWG) – bad composts to which nothing (Control), 20% topsoil (S) or topsoil (20%) plus coal fly ash (10%) (SA) had been added.
Treatment Bulk density
(m m-3)
Total
porosity
Available
water
EC
(mS cm-1)
Extracable
P
阅兵 英文Germination
index (m3 m-3) (kg m-3) (mg kg-1) (%)
GW(control) 0.29a a 0.83d 133a 1.1b 616b 94bc
GW(S) 0.69d 0.70b 190ab 0.62a 212a 117c
GW(SA) 0.69e 0.66ab 273c 0.61a 183a 119c
GWP(control) 0.35b 0.79c 171a 1.1b 553c 85b
hotmailGWP(S) 0.58d 0.71b 258c 0.60a 228a 116c
GWP(SA) 0.69e 0.65ab 299c 0.64a 186a 145d
GWG(control) 0.35c 0.76c 129a 2.8e 2771f 54a
water heaterGWG(S) 0.66de 0.68b 174a 1.6d 1250e 57a
GWG(SA) 0.76e 0.64a 225b 1.3c 894d 61a
Means followed by the same letter within a column are not significantly different at p≤0.05
employerComposted green waste was characterized by a low bulk density and high total porosity (Table 1). The high macroporosity and relatively low available water holding capacity may limit its u in a field landscaping situation (Belyaeva and Haynes, 2009). The greater intensity of microbial decomposition induced by addition of poultry manure or grea trap waste/ptage to green waste tended to result in a greater percentage of small particles being produced and this caud an increa in bulk density and a lowering of total porosity (Table 1). When added to the composted green waste, fine soil material (i.e. originating from a silt loam) and/or coal fly ash partially filled the macropores of the green waste resulting in an increa in bulk density, decrea in total porosity and an increa in percentage mesoporosity and thus available water holding capacity (Table 1). The substantial increas in available water holding capacity that resulted are likely to be of considerable benefit when the material is being ud in a field landscaping application, particularly in the Australian context where droughts are common and most cities currently have water-u restrictions in place.
High concentrations of extractable P are a characteristic of green waste composts (Hue et al., 1994; Belyaeva and Haynes, 2009) becau organic material has insignificant P-sorption capacity and therefore a relatively large proportion of their total P content (e.g. 30-40%) is extractable and potentially bioavailable. Concentrations of extractable P (Table 1) encountered in the GW and GP alone composts (183-616 mg kg-1) are excessive whilst tho in the GG compost are extraordinarily high (2771 mg kg-1). The levels may well be harmful to plants, particularly Australian native plants that are adapted to low available P conditions. Handreck and Black (2002), for example, suggested optimum Colwell P levels were < 10mg kg-1 for native plants nsitive to P and < 40 mg kg-1 for plants moderately nsitive to P. Similarly, soluble salts (EC > 1.3 mS cm-1) were extremely high (Table 1) and large concentrations of NH4+ and NO3- were also prent in the GWG composts. That is, concentrations of NH4+-N ranged between 69 and 227 mg kg-1 and NO3--N between 68 and 80 mg kg-1 in GWG composts compared with between 1.9 and 14 mg kg-1 for NH4+-N and 0.26- 0.68 mg kg-1 for NO3--N in the other two composts (data not shown). The high levels of salts, P and mineral N probably all contributed to the low GI (< 60%) for the GWG composts. Thus, the high salt, P and N content of the grea trap waste/ptage resulted in accumulation of the substances in the GWG compost. Values of GI less than 100% were also recorded for the GW alone and GWP alone composts and the were probably related to high soluble salts (> 1.0 mS cm-1) and high extr
actable P (> 500 mg kg-1) levels. That amendment of GW and GWP composts with soil or soil plus ash resulted in GI values > 100% demonstrates the importance of such amendment with regard to producing a suitable substrate for plant germination and growth. Such amendment lowers EC and extractable P (Table 1) by dilution and in the ca of P also by adsorption. That is, both soil and fly ash contain mineral surfaces (e.g. Al and Fe oxides and aluminosilicates) that can specifically adsorb phosphate.
Conclusions
Green waste is an effective adsorbent material for grea trap waste/ptage and the material composts rapidly at thermophilic temperatures. The resulting compost does, however, contain excessive levels of extractable P, high soluble salts and mineral N levels. There ems scope to dilute the grea trap/ptage-amended compost with unamended green waste compost in order to lower soluble salts, extractable P and mineral N in the saleable product. Addition of inorganic materials such as subsoil or fly ash to composted green waste has veral important positive effects including increasing available water holding capacity and reducing excessive concentrations of soluble salts and P that may have accumulated.
References
Belyaeva ON, Haynes RJ (2009) Chemical, microbial and physical properties of manufactured soils produced by co-composting municipal green waste with coal fly ash. Bioresource Technology 100, 5203-5209.
Bradshaw J, Lehmann TR, Ragsdale J, Snow C (1996) Recycling Yard Trash: Best Management Practices Manual for Florida. (Florida Organics Recyclers Association, Tallaha, Florida).
Brewer LJ, Sullivan DM (2003) Maturity and stability evaluation of composted yard trimmings. Compost Science and Utilization 11, 96-112.
Coker C (2006) Composting grea trap wastes. BioCycle 47, 27-30.
Colwell JD (1963) The estimation of the phosphorus fertilizer requirements of wheat in southern New South Wales by soil analysis. Australian Journal of Experimental Agriculture and Animal Husbandry 3, 190- 198.
Francou C, Lineres M, Derenne S, Le Villio-Poitrenaud M, Houot S (2008) Influence of green waste, biowaste and paper-cardboard initial ratios on organic matter transformations during composting.
Bioresource Technology 99, 8926-8934.
Handreck KA, Black ND (2002) Growing Media for Ornamental Plants and Turf. (NSW University Press, Randwick).
Hue NV, Ikawa H, Silva JA (1994) Increasing plant-available phosphorus in an Ultisol with a yard-waste compost. Communications in Soil Science and Plant Analysis 25, 3291-3303.中文转换日文
Isbell RF (2002) The Australian soil classification. (CSIRO Publishing, Collingwood, Victoria).
Manr AGR, Keeling AA (1996) Practical Handbook of Processing and Recycling of Municipal Waste.
(CRC Press, Boca Raton).
Wakelin NG, Forster CF (1977) An investigation into microbial removal of fats, oils and greas.
Bioresource Technology 59, 37-43.
Zaccheo P, Ricca G, Crippa L (2002) Organic matter characterization of composts from different feedstocks.
thirtyCompost Science and Utilization 10, 29-38.
Zucconi F, Monaco A, Forte M, De Bertoldi M (1985) Phytotoxins during the stabilization of organic matter.
In: ‘Composting of Agricultural and Other Wastes’. (Ed JKR Gasr), pp 73-85. Elvier, London.
