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On-farm Composting of Municipal and Commercial Organics as an Environmentally and Socially SustainableResource Recovery Scheme for Rural Communities

June 2003,
Environment Australia


Executive Summary

The Organic Force, in cooperation with Crows Nest Shire Council, was successful in obtaining funding through Environment Australia's Recycled Organics Initiative to assess the merits of On-farm Composting of Municipal and Commercial Organics as an Environmentally and Socially Sustainable Resource Recovery Scheme for Rural Communities. The project proposal was prompted by a situation where waste management and resource recovery in rural and regional areas had not received much attention from Government agencies and where councils that wanted to offer recycling services had no alternative other than implementing the 'standard' kerbside recycling of dry recyclables. This system was developed for urbanised population centres and was not necessarily the most appropriate recycling system for rural/regional communities. The waste management and resource recovery situation in these areas is profoundly different to that in urban areas.

The collection and subsequent composting and beneficial use of municipal and commercial organics at local farms was seen as a particularly promising alternative to conventional kerbside recycling in rural/regional areas, as it offered a wide range of potential benefits that underscored the notion of sustainable development. Expected benefits include

Apart from assessing the technical and financial feasibility of the proposed organics recycling scheme and evaluating community perceptions, the project set out also to improve current disposal practices for septage (pump-out) collected from residential properties.

The project was conducted in Crows Nest Shire, which is located approximately 170 km west of Brisbane, just north of Toowoomba. The closure of the Crows Nest landfill due to leachate threatening to contaminate Toowoomba's drinking water supply made council aware that their 'tips' could pose considerable risk to the well-being of humans and the environment and consequently be the cause of significant liability claims. This experience convinced Crows Nest Shire Council of the need to improve its waste management practices and to look for alternatives to the existing system.

Situation in Crows Nest Shire

Crows Nest Shire has approximately 10,300 residents who live in 4,200 households. 3,000 households receive a weekly waste collection service, 2,071 receive a fortnightly recycling service (240L bin) and 1,200 households receive no service.

In 2000/01 about 1,650 tonnes of waste was collected from the kerbside, representing 550kg per household per year. Kerbside collected waste that was analysed at the outset of the project contained 54% organic materials in more rural dominated areas and 62% in more suburban dominated areas. Regardless of the collection service, a considerable amount of waste was also taken to the six disposal facilities within the shire. Estimates for the amount of waste disposed of annually at landfills within the shire ranged between 5,500 tonnes and 7,200 tonnes. Of this, kerbside collected waste represented 30% at best. Most waste delivered to landfills originated from private households (86%), while commercial and industrial waste comprised only 14% by volume (v/v). Envirocom's audit of waste deliveries to a landfill in the shire showed also that approximately 66% (v/v) of all disposed materials was organics. 50% was comprised of garden organics, which were taken directly to a designated disposal area. Segregated garden organics are currently burnt, an activity sanctioned by EPA.

In 2000/01 some 283 tonnes of recyclables were collected. This corresponds to a recycling yield of 137kg per household per year and a recycling rate of 19.9% for those who are offered recycling services. If all kerbside collected material is considered, the recycling rate drops to 14.7%. Recyclables collected in Crows Nest Shire contained relatively low contamination levels compared to a 20% regional average, which is mainly due to the use of split bins in other areas.

Before the organics recycling project was publicised and promoted, a survey of shire residents sought to establish current waste management and recycling activities, the level of satisfaction with existing services and desired future waste management and recycling developments. It was found that home composting was the most popular form of recycling, except for the kerbside recycling service, which is compulsory in areas where it is offered. 83.3% of households across the shire claimed to practise home composting as a means of recycling. The use of charities to dispose of re-usable or recyclable goods was also very popular. Drop-off recycling was less popular, regardless of whether receptacles were located in the neighbourhood or at landfill sites. Organic materials most commonly used on-site for mulching and composting included grass clippings, raw fruit and vegetables and tree/shrub prunings. Overall, it appeared that households that received no service were best in utilising organic materials 'on-site'. Asked about their level of satisfaction with the existing recycling and waste management services offered, most households (97.4%) that received both waste and recycling collection services felt that the provided services were either satisfactory or more than adequate. On the other end of the scale, 86.7% of residents that received no service were not satisfied with the current situation and would like to see improvements. Between 43% and 47% of households across all three service levels stated their willingness to pay between $2 and $5 per month more for improved (recycling) services. With regard to potential future recycling and waste management developments, most shire residents saw an increase in waste reduction initiatives (77%) and improved support for home composting (75%) as popular future options. On-farm composting, introduction of the 'user-pays-principle' and kerbside collection of organics would be also acceptable within the shire (approval ratings above 50%). On the contrary, a large scale processing facility, alternating weekly waste and recycling collection and a new landfill would not find much support among shire residents.

A survey of local businesses that were prone to generate organic waste showed that organics contents ranged between 5% and 99%. Three-quarters of the interviewed businesses were prepared to segregate their organic waste materials if there were a dedicated organics collection, and many of them seemed to be doing so already. Some companies were willing to pay extra for a dedicated organics collection and some envisaged potential savings by extending the collection interval of their waste bins. Due to the use of organic residues as animal feed or for mulching and composting, businesses often considered the level of organics in the waste stream too little to be concerned about. Nevertheless, co-collection of commercial organics should be offered to interested businesses as this would increase yields and improve collection efficiencies.

Establishing the Highfields Organic Recycling Project

An area in Highfields with 386 residential homes was selected to establish and assess the kerbside collection of garden and kitchen organics. The organics collection was free and participation was voluntary for residents in the trial area.

Proper education and motivation of residents were considered to be of utmost importance for the success of the organics collection scheme. Subsequently, a staged and intense information and education campaign was conducted. The information campaign used mass media, including the council newsletter, to inform the general public about the trial. The education campaign targeted householders in the trial area and provided specific information related to the collection of the organic material and its further processing and use. The staged education campaign was comprised of:

Each household in the trial area received an information brochure and a 5L kitchen tidy bin, regardless of whether they participated in the trial or not. 319 out of the 386 households in the trial area, or 82.6% were willing to participate in the Highfields Organic Recycling Scheme and were provided with a 120L organics recycling bin. The small 120L bin was used because the contractor did not supply the desired 240L bins.

Garden and kitchen organics were collected fortnightly between April and November 2002. The amount of collected material fluctuated between 1,100 and 2,400kg per fortnight, averaging 1,680kg. Winter and intensifying drought conditions reduced collection yields. However, low presentation rates (60%-65%) were also a major factor in collection yields that were lower than expected. A survey tried to identify problems that caused the low presentation rate but little could be done to improve the situation. The main problems identified were that the bin was too small, that collection was not on the usual day and that there was odour from the kitchen tidy bin. The survey showed that 9% of households didn't use their bin and 23% put it out only occasionally.

However, on the other hand, quality of the collected material was excellent with impurity levels of only 0.3%. There was also virtually no material that exceeded the specified maximum size (Ö< 2.5cm). This excellent result was attributed to good public education and delivery of the organic materials to a local farm.

On-farm Composting

Selection criteria for the establishment of on-farm composting were developed in order to facilitate the search and selection of suitable farms. The selection criteria addressed the following aspects:

Commercial composting operations in Queensland with a design production capacity of more than 200 tonnes per year require a licence. If the composting operation is to be established at a feedlot or piggery, the Department of Primary Industries is the responsible authority, for all other farmers it is the Environmental Protection Agency. However, no license is required for on-site or on-farm composting of own and imported organic materials as long as all of the finished compost is utilised on-site (i.e. on the farm) and not sold for commercial gain. Charging of a gate fee to cover processing costs is not seen as 'commercial gain'.

The composting operation used in the trial did not require a licence because it was designed to process less than 200 tonnes per year and also because the finished compost was not sold for a profit.

The on-farm composting operation was established at a 320hectare organic dairy and chicken farm that was willing and suitable to participate in the project. The composting area was established close to dairy effluent ponds for access to irrigation water and the devised simple composting system could be operated with existing machinery, required little additional investment and was simple to manage and operate. The delivered organic material was not shredded prior to being composted in order to keep operating costs low. This was possible since residents did not dispose of branches or wood that exceeded 2.5 cm in diameter.

The devised simple on-farm composting system consisted of a 'perpetual windrow' to which new material was added at one end (tipped directly from the collection vehicle) and mature material was removed from the other end. Once the collected organics were delivered and the impurities removed, the new material was covered with chicken manure (sawdust based) and pond sludge (from dairy effluent ponds) so that no foodstuff was exposed. The material was turned for the first time after two weeks. This procedure was adopted in response to concerns raised about the possibility of farm or wild animals picking up foodstuff and spreading diseases. Subsequently, the windrow was turned every two weeks with a tractor front-end loader. Once the composting process was nearing completion after some six months, older sections of the 'perpetual windrow' were pushed into mounds for curing and maturing. The material was composted for prolonged periods to break down the coarser feedstock and newspaper packs used to wrap kitchen organics. This was necessary since the finished product was not screened before land application.

Processing of unshredded material and use of a front-end loader for turning made the removal of impurities relatively easy. However, the use of a dedicated (tractor-driven) windrow turner would certainly improve mixing of different feedstock materials and would also aid breaking up of coarser feedstock components (twigs and branches).

Due to ongoing blocking of pipes and an unwillingness to invest in a pump, dairy effluent was not used to irrigate the windrows.

Even though the farmer fully supported the project, composting was not his core business and did not have a very high priority. Understandably, staff and machinery were allocated first of all to accomplish farm related tasks and compost related tasks were secondary. The limited scale of the trial fostered this approach as it provided only little additional income for the farm. This unfortunately resulted in situations where the composting operation did not receive as much attention as required, and particularly the relatively labour intensive task of irrigating the windrow was neglected. Consequently, at times the material was relatively dry and the composting process slow.

Nevertheless, temperature records show that the process was sufficient to eliminate pathogens and weed seeds. The prolonged composting process also aided pasteurisation.

The composting process employed during the trial was designed to produce fully matured compost even though pasteurised products can be used in agricultural applications. Nutrient levels of the generated compost were typical for products that originated from garden organics, i.e. relatively low in nitrogen but sufficient in other macro and micro nutrients. Low pH and high conductivity levels however, were unusual and could not be fully explained. It was noted that heavy metal limits stipulated for Grade A product in the NSW EPA Biosolids Guidelines were considerably lower than levels in manures and fertilisers allowed in the Organic Production Standards (Biological Farmers of Australia [BFA]).

Compost Use

Compost should be used in accordance with good agricultural practice. This means that the applied compost should be fit for purpose, should not have excessive contamination levels and the rate and timing of applications should be in accordance with plant nutrient requirements and with consideration to environmental conditions. Nutrients provided through the use of compost need to be accounted for in nutrient budgets for individual crops as well as for the entire cropping sequence. High application rates of nutrient rich compost and inadequate timing of compost application can result in detrimental environmental effects through leaching and ground water contamination. The NSW EPA Biosolids Guidelines set the maximum agricultural application rate at 1,200kg nitrogen per hectare (for other than Grade A products) while the BFA organic production standard recommends an application rate of 20 tonnes (fm) per hectare. A comparison between the amount of nutrients supplied by 20 tonnes of compost and nutrients removed by a wheat or barley crop demonstrated that compost was able to supply more than sufficient phosphorus and potassium and contribute towards supplying the required nitrogen. Additional nitrogen has to be supplied by other means to meet nutrient demand of agricultural crops and facilitate high yields. Compost is considered ideal for organic farmers. They can replenish nitrogen relatively easily, but not other plant nutrients such as phosphorus or sulphur: these can be supplied by compost derived from external sources.

Based on literature data, compost made from garden and kitchen organics was valued at about $40 per tonne (dm) for nutrients (N, P, K, Mg, Ca) and organic matter found in the generated product.

Costs of On-farm Composting

The scale of the composting activities during the trial was too small to provide meaningful information about operating costs and economic outcomes for on-farm composting. Nevertheless, investment and processing costs were determined for three hypothetical on-farm composting operations that processed 1,000 tonnes, 5,000 tonnes or 10,000 tonnes of municipal / commercial organics per year. It was assumed that each facility used open windrow composting on a hardstand area but used different machinery for turning and handling, i.e. tractor front-end loader, tractor driven windrow turner and a wheeled loader (second hand). Accordingly, investment costs ranged between $25,000 and $175,000, most of which was dedicated to the hardstand (Table I). While absolute investment costs increased for the larger plants, investment costs per tonne design capacity decreased.

Table I Investment costs ($) covering site works and equipment for on-farm composting operations with various processing capacities
Item / Service
Design capacity
1,200 t/yr
1,200 t/yr
5,500 t/yr
11,000 t/yr
Civil construction *
21,617
17,232
48,375
88,464
Windrow turner
-
35,000
35,000
35,000
Retrofitted bucket + misc.
3,500
3,500
4,000
2,000
Loader (second-hand)
-
-
-
50,000
Total investment
25,117
55,732
87,375
175,464
Investment / t capacity
20.93
46.44
15.80
15.95
* Mainly hardstand for composting & storage, incl. planning and design

It should be noted that neither costs for size reduction (shredding) of the feedstock nor for screening of the composted material are included in these cost calculations. Trial results show that these costly processing steps are not required, provided the feedstock quality is high. If the feedstock contains only few or no large wooden components and few impurities, shredding and screening will not be necessary. Processing costs will increase considerably if either or both of these processing steps are necessary.

Processing costs for the assessed hypothetical composting operations ranged between $8.50 and $21.60 per tonne if all costs were borne by processed municipal organics (Table II). If return on investment is taken into account, gate fees for municipal and commercial organics can be determined; they range between $10.30 and $26.80 per tonne.

Table II Summary of processing costs ($) for on-farm composting operations with various processing capacities
Criteria
Scenario / Design capacity
1,200 t/yr
1,200 t/yr
5,500 t/yr
11,000 t/yr
Total processing costs / year
21,579
21,235
48,035
85,094
Costs / t processed organics
17.98
17.70
8.73
7.74
Costs / t municipal organics
21.58
21.23
9.61
8.51
Costs / m3 generated compost
20.30
19.98
10.22
9.05

Compost application costs were not considered. It is suggested that they can vary between $3.50 and $9 per tonne. It could be argued that the farmer should cover application costs in return for the value of the compost that was applied.

Assessment of Organics Recycling Scheme

The presentation rate for organic recycling bins was relatively low at 60%-65%. Approximately 73% of households that were provided with a bin were firmly committed to the organics recycling scheme and used their bin regularly. Given the initial participation rate in the voluntary scheme of 82%, it infers that about 60% of all households in the trial area used the system.

Kerbside collection of organics reduced the volume of waste disposed of via the grey bin. On two occasions, the average filling level of grey bins in the trial area (i.e. users and non-users of the organic recycling bin) was lower (by 11% and 13.5%) than for bins in the non-trial area. On visual inspection they also contained less organic material.

Two waste audits were conducted and results compared to benchmark figures established at the outset of the project to assess the reduction of organic materials in the waste stream and the amount going to landfill. While garden and kitchen organics fluctuated between 45% and 54% in waste from Crows Nest, organic components in waste from Highfields declined from 63% to in September 01 to 43% in November 02. However, a comparison between the trial and the non-trial areas showed only slightly lower organic levels in waste generated in the trial area, even though the organic material represented approximately 18.4% of the total amount of material collected from the kerbside in the trial area.

Unfortunately, the contractor could not provide adequate weighbridge data that could be correlated with waste audit figures. This greatly hampered the accurate assessment of the effectiveness of the organics recycling scheme in reducing organic material going to landfill. This situation demonstrated that waste composition figures alone are of limited value and can give misleading results. Waste composition figures are only able to reveal the relative composition of mixed waste materials but do not provide any quantitative information. A true picture can be provided only if waste composition data are correlated with accurate weighbridge information.

On average, the fortnightly organics collection yielded 1,680kg. This represented an annual collection yield of about 137kg per household and 57kg per capita if all 319 households that received a bin are taken as a basis. If collection yields are assumed to have been generated only by those households that participated actively in the scheme (75% or 240 households), annual collection yields per household and per capita would increase to 182kg and 76kg, respectively. These figures compare favourably with those achieved by the standard recycling collection (Table III), which yielded 141kg per household per year or 59kg per person per year. This is even more so if conditions are considered in which the organics collection took place, i.e. voluntary scheme, small bin, unusual collection day, collection during the winter period and in drought conditions. In areas such as Highfields, the collection yield under normal circumstances is expected to be in excess of 100kg per capita per year.

Table III Comparison of collection results for kerbside collection of dry recyclables and organics
   
Dry recyclables
Organics
Quantity collected per year / fortnight  
291,200kg*
1,680kg
No. of services / bins delivered  
2,071
319
Proportion of bins used and emptied  
100%(2,071 bins)
100%(319 bins)
75%(240 bins)
Quantity collected per household per fortnight
kg/household/fortnight
5.41
5.27
7.00
Annual quantity collected per household
kg/household/year
140.61
136.93
182.00
Annual quantity collected per capita **
kg/capita/year
58.59
57.05
75.83
* Based on two audits in Highfields in October and November 2002, assumed to represent 65% of all services
** Based on average of 2.4 people per household

Costs and Economics

Current costs for the collection of waste and recyclables (including costs for sorting) are shown in Table IV. Collection and sorting of dry recyclables amounts to $268 per tonne and $38 per household per year. This compares to waste collection costs of $46 per household per year.

Table IV Collection costs for waste and recyclables in Crows Nest Shire
 
Costs *
 
per year
per tonne
per hh
 
$/year
$/t
$/hh
Waste collection
137,685.60
77.40
45.90
Recycling collection **
78,044.39
268.19
37.68
* service charge includes provision and maintenance of bins
** includes sorting of co-mingled recyclables at Materials Recycling Facility in Toowoomba

Collection of organics during the trial was charged at a very high rate ($1.59 per bin per collection). Collection costs would be substantially lower if organics were collected regularly and on a larger scale.

Processing (sorting) costs for recyclables were assumed to range between $125 and $165 per tonne while costs for on-farm composting are expected to be between $10 and $25 per tonne.

Current operating costs for all disposal sites in the Crows Nest Shire amounted to almost $183,000 per year. Depending on the quantity of waste disposed of in the shire (5,500 vs 7,300 tonnes) landfill operating costs range between $25 and $33 per tonne. It is pointed out that full costs of a landfill are considerably higher than the mere operating costs.

Resident's experience

The experience with the organics recycling scheme and the level of support were assessed through a telephone survey of 143 households, equally split between participants and non-participants in the Highfields Organic Recycling Project. For residents that participated in the trial, the information brochure was the most important source of information. The council newsletter was also important in providing information and the doorstep visits seemed to reach about 60% of all households. Once organic recycling bins were provided, most households (66.1%) used the collection system to recycle raw fruit and vegetables. The most popular garden materials collected were weeds and dead plants (64.4%), leaves (55.9%) and tree prunings (49.2%). Only one third of households recycled lawn clippings in this way. Overall, the organics recycling system worked well with two-thirds of all participating households not experiencing any problems. While 31% of households did experience problems or difficulties with the organics collection scheme, more than half of these (52.6%) were unhappy about the small organics recycling bin. 31.6% of problems were related to odour and 21% to flies/maggots, which represent 9.8% and 6.6% of all participating households respectively.

With reference to the current development of a waste management strategy, residents were asked whether they would approve or disapprove of specific recycling and waste management options. Approval rating for most proposed options was relatively high, regardless of whether it concerned improved support for home composting (average of 90%) or establishment of a new landfill site (average of 76%). A survey at the beginning of the project provided responses to the same question that were a lot more differentiated and approval ratings generally were considerably lower. More users than non-users of the organics recycling scheme supported local on-farm composting (96% vs. 79%), while the reverse was the case for the user-pays system (57% vs. 75%). Across the board, the following three proposed activities received the highest approval ratings:

Kerbside collection of organics received an average approval rating of 89.4%. People who had gained first-hand experience with the organics recycling scheme were more willing to be part of such a scheme than those who had only heard about it. Including conditional consent (yes, if…), 91.1% of organic recycling scheme users would be willing to participate in a future organic recycling scheme while only 70.8% of non-users showed the same preparedness. This demonstrated that residents were happy with the organics recycling scheme and that none of the problems encountered during the trial were seen as major deterrents. However, the reduced support for personal participation of residents who had no first-hand experience suggests that there are misconceptions and prejudices about this type of organics recycling scheme within the community.

Comparison of recycling systems

The two recycling systems, i.e. collection of dry recyclables and organic materials were compared by modelling the expansion of recycling services to 1,000 households in Crows Nest Shire. Three scenarios were considered:

1   Existing recycling scheme for dry recyclables;

2-A   Organics recycling scheme that reflects conditions as they existed during the trial, except for collection and processing costs;

2-B   Good organics recycling scheme

Scenarios 1 and 2-A were expected to divert approximately 140,000kg of waste per year from landfill, while the good organics collection scheme would divert about 240,000kg, 71% more.

Combined collection and processing costs were considerably lower for the collection of organics than for dry recyclables. While the collection and sorting of dry recyclables would incur annual costs of $37,684, collection and processing of organic materials would cost $26,373 and $28,828 for Scenarios 2-A and 2-B, respectively. Annual costs per household would amount to $37.68 for collection of dry recyclables and to $26.37 (Scenario 2-A) or $28.83 (Scenario 2-B) for collection of organics.

Total costs for the collection and composting of organics depend on the quantity of collected materials and gate fees charged per tonne. With collection yields between 60 and 100kg per person per year and gate fees between $10 and $25 per tonne, annual processing costs for kerbside collected organics in the Crows Nest example could vary between $1,450 and $6,000 (Table V). Depending on these factors, the organics collection system would cost between $8,700 and $13,300 less than the collection and processing of dry recyclables and hence provide annual savings between $8,700 and $13,300 to council ($8.70-$13.30 per household).

Realised savings by adopting the organics recycling system could be used in the following ways:

From a recycling and resource recovery point of view, the two latter options would be preferable as they would result in a situation where, compared to the existing recycling scheme, the same amount of money would provide for significantly improved outcomes, namely

It is proposed that new integrated waste and recycling collection schemes would combine collection services for municipal and commercial waste and recyclables as far as possible.

Table V Potential savings offered by organics recycling scheme (1,000 services)
Collection costs
Costs / collection
Collections / year
Costs / year
 
($)
 
($)
Dry recyclables
1.45
26
37,684
Organic materials
0.88
26
22,948
Potential savings
14,737
Organics processing
Possible yield
60-100kg/capita/yr
Possible gate fee
$10-$25 / tonne
Possible processing costs
$1,450-$6,000 /yr
Potential annual savings
$8,737-13,297 / year

Recommendations

Based on the outcomes of this project it is recommended that local authorities in rural and regional areas focus their recycling activities on organic materials and consider advancing and implementing an integrated recycling strategy with the following components:

  1. Segregation of coarse garden organics at dedicated, supervised drop-off sites; material is shredded, possibly pasteurised and used predominantly as mulch.
  2. Kerbside collection of fine garden organics and selected kitchen organics (optional), material is processed through on-farm composting and utilised in agricultural applications.
  3. Collection of dry recyclables (paper, glass, metal, plastics) through high-yielding drop-off scheme.
  4. Collection of waste in bins smaller than 240L, or at extended collection intervals, e.g. fortnightly, alternating with the organics collection.