Centemero M.**, Ragazzi R*., Favoino E.*

1. ABSTRACT

Scope of the document is to analyse the agronomic characteristics of the different qualities of compost produced and the way they fulfil (or not) the quality requirements needed by the potential end users (e.g. farmers, landscapers, plant breeders, vine-growers, etc.). The total amount of the current compost production and its application are reported as well. Finally the document provides suggestions on what has to be done to regulate, promote and develop the compost market: labels, quality limit values according to specific features in the different end-use sectors.

2. INTRODUCTION

Traditionally the use of soil improvers in agriculture is aimed at the restoration of the organic substance removed from the agro-ecosystem by crops. The addition of humus, as replacement for the portion gradually mineralised by the micro-organisms of the soil, leads to the conservation of its fertility under many point of view: physical (e.g. porosity, drainage, aeration), chemical (availability of nutrients) and biological (intensity of the microbial activities) fertility of the soil itself. In such a respect, the amount of nutrients in a compost is seen as a positive and significant characteristic because the nutrients released during compost degradation get available for the vegetable needs. On the other end, the nitrogen concentration could be a limiting feature referring to maximum nitrogen load.

A different evaluation has to be done for other sectors such as horticulture, floriculture, fruit culture, tree nursery where compost is mainly used as growing media in potting. In this case the main feature to be assessed are properties such as total porosity, hydrophily, permeability, conductivity of water solutions.

Thus, it is possible to identify two different main uses of the composted products:

• as soil improvers
• as growing media

Starting from the evaluation of specific technical features for the composted materials and comparing them to the traditional fertilisers, it is possible to define marketing opportunities and technical conditions to promote the use of composted products.

3. MATERIALS AND METHODS

Since several years, Scuola Agraria del Parco di Monza has run technical surveys and data banks about composting. Beside, research programs about process management and optimisation of source separated systems, as for quality and marketing. The main fields of investigation have been: actual and potential market for composted products, amounts, quality and uses of the composted produced, chemical-physical analysis of the available traditional organic fertilisers comparison to composted materials. Some of the collected data will be shown further in this document. Other sources are listed in the references.

     4. COMPOST QUALITY

4.1 Product analysis of the composted products

Table 1 and Table 2 show an analytical comparison of main agronomic parameters between traditional organic fertilisers and different compost products. The source is the data bank held by Scuola Agraria del Parco di Monza and University of Milan, dept. of Physiology and Agro-chemistry. The data bank refers to approx. 500 samples of fertilisers commercialised in Italy.

Table 1 Chemical-physical parameters and heavy metals content

* produced with the suitable addition of a percentage of bulking materials (barks, tree prunings, wood chips, etc.)

Table 2 Micro-nutrients and physical-hydrological parameters

Table 1 and Table 2 show that:

• yard waste compost
  Fully accomplishes agronomic requirements and has favourable physical and chemical characteristics. In particular, salinity of is lower than salinity of manure: avoid any potential damage to the plant roots. As a consequence, this product is suitable for the preparation of specific growing media for the nursery sector. The weak point of yard waste is its low content in nitrogen, phosphorus and potassium. In this case, given the poor release of nutrients during the organic matter degradation in the soil, the main contribution of yard waste compost is its function as soil improver: it has to supply humus to improve physical, biological and structural properties of soils poor in organic matter.

• Food and sludge compost
  They guarantee humus supply as well as a relevant supply of nitrogen, phosphorus, potassium and micro-nutrients. The main fields of application for such products with a high nutrient release are:

1. horticulture sector
2. crops at the beginning of rotation
3. new plantations in viticulture and fruit culture.
4. organic farming, as it practices, in general, only the organic fertilisation, not the chemical one.
5. gardening and landscaping, especially during the construction of gardens or landscapes in recent urbanised areas.

The high salinity content of food and sludge composts, measured through the electric conductivity, limits their use in the nursery sector that produces plants in pot. Or, at least, claims for a blending with peaty materials.

Anyway, it has to be stressed a basic difference between ‘food waste’ collected in Italy and ‘bioabfall’ waste collected in Germany, Austria (or the VGF waste addressed in the Netherlands). In Italy, as in other Mediterranean situations (e.g. Spain), source separation systems target mainly food waste with an intensive door-to-door collection and tools to promote proper behaviour among households (e.g. use of watertight bags). Green waste delivery is not allowed, in general, in the same bin as food waste. Households may either take it to a Municipal Recovery Centre or home-compost it (Favoino, 1999 a, in press b). The general outcome is a feedstock mixture with, in general, a higher percentage of food waste as compared to German, Dutch, Danish, Austrian, situations, where in ‘Bioabfall’ a major percentage of yard waste is delivered.

As a result, there are market differences as for main analytical features such as nitrogen content, salinity, with the ‘Italian’ mixture being much closer to food waste features than feedstock in Central Europe (that is closer to yard waste features).

4.2 Specific quality requirements in different agronomic sectors

The use of organic materials aims at improving the physical, chemical and biological characteristics of the soil. The substance traditionally used was manure, at different stages of maturity, according to specific needs and availability. The manure was provided by animal breeding in the farm themselves. Since several years, in some European countries (and namely in Italy) the farm structure has been changed and the activities of animal breeding and crop cultivation got separated. The consequence is a relevant lack of organic matter which is to be supplied to the soil especially in those areas where viticulture, fruit culture, horticulture, rice and citrus fruit growing are highly specialised. This is on itself an important chance for the technical valorisation of the composted products. These opportunities are much more interesting thanks to the great potential demand, and to analytical requirements that are perfectly fitted by composts from source separated organic waste.

The requirements for these composting products are:

• A good content of organic matter
• A satisfying degree of ‘stability’ in some cases (e.g. in horticulture for the fertilisation between two subsequent cultivations, in tree and fruit culture during preparation of the plantation hole of new trees).
• A medium refining degree: sieving between 10 and 20 mm is enough to guarantee a suitable size and homogeneity of the material.

Due to weather and cropping conditions, the lack of organic matter in the Italian and Mediterranean soils, claims for a huge potential need of composted products from source separated organic waste. Still, the possibility to rally apply it is conditioned by the competitive availability of manure.

In this sector, also the price gets influenced by manure. In fact, compost is considered as a surrogate for manure and its value (and price) is linked to the value of manure. This leads to some difficulties since, it is not usual to have a market for manure; in traditional farming, manure is produced by the farmers themselves trough animal breeding and there is no need to buy it outside. So it is often difficult for the farmers to give manure a price. A market for manure can be found only in some peculiar local conditions and prices range from 5-15 to 25-30 Euro/t . A part from manure, some other hindrances can be found in:

1. A lack of confidence by farmers towards any material coming from ‘urban’ waste;
2. the need of proper machines to spread compost; in fact the equipment normally used by farmers (i.e. fertiliser spreaders and slurry spreaders) only deals with organic or mineral fertilisers with higher humidity content or different granulometry. Thus, compost application claims for new machineries.

These sectors are related to specialised open field cultures that provide high incomes. The intensive crop rotation leads to a remarkable soil depletion of nutrients and organic matter.

Therefore, considerable amounts of organic fertilisers are needed at the beginning of the cultivation and during plant growth.

In this context, the Trade Associations (i.e. beet-growers, vegetable growers, fruit growers, etc.) define the quality requirement of composts that, in turn, influence compost’s prices.. The technical conditions that influence the market price of compost are:

1. characteristics of the traditional fertilisers
2. technical possibility to surrogate fertilisers with compost
3. logistics and transportation
4. availability of effective compost spreader equipment

This sector includes all hobby and professional activities dealing private and public green areas (e.g. gardens, parks, landscapes). In fact, during last years, gardening and landscaping have undergone a remarkable development thanks to the arising attention paid to the quality of urban spaces, to the research of a better balance between building construction and green areas and to the increased time for hobbies. This brings to forecast a significant steady growth in the number of those interested in the use of traditional and innovative organic materials.

Technical and economical conditions promote the use and sell of quality composts particularly in these two sectors for the following reasons:

1. better incomes of the soil improvers and fertilisers in these sectors as compared to the traditional field crops;
2. ‘operational proximity’ between composting plants and garden centres/nurseries. It has to be underlined that gardeners themselves are large producers of green waste that have to be delivered to the composting plants. Therefore, they ‘know the source and the process’ and are much more ready , as compared to farmers, to accept and ask for compost.
3. Possibility to propose materials of different quality and price according to different specific use such as gardening, top-dressing, nursery, etc.

Different characteristics are required to the composing product according to the uses:

• Gardening

in this case the organic fertiliser is primarily seen as soil improver to add humus to the soil. Therefore, its analytical requirements are: quantity of organic matter in form of humus and a low humidity is preferred.

If compost gets in direct contact with seeds or roots (i.e. used as bed for grass-sowing grass or to fill up the plantation hole of soil-less plants). Main requirements are the full ‘stabilisation’ of the material that must comes out from a long curing period and a low salinity (not above 1500-2000 m S cm^-1). The low salinity content is easily guarantee by green waste compost, only seldom by compost from food waste because of the salt used for cooking. This second type should be analysed of the specific electric conductivity that influence the blend with other materials.

In case of spreading on large areas, as well as in field crops, it is not required a long curing stage because compost is used as surrogate for manure to supply organic matter to the soil. The main point is the content of nutrients and the balance between them. That is why, the compost from food waste, with an high nutrient supply, is recommended for this use.

• Land reclamation, exploited mines and landfill sites

These soils poor in structure need compost mainly as soil improvers to regenerate the physical and chemical properties as well as the biological activity. Given that a large amount of compost is needed, it is important that the mineral content of the compost used is quite low to avoid ecological damages (i.e. nitrate leakage in the ground water)

• Nursery and plants in pot

The traditional plant substrate in this case is peat. Peat is mixed with different organic and mineral materials (e.g. sand, clay, long-term release fertilisers, etc.) in order to improve the substrate structure, change or buffer the pH value, supply nutrients according to the needs of the plants and the specific cultivation techniques.

The specific requirements for these substrates are: good porosity, reversible hydrophilic conditions, resistance to compression, low salinity, full stabilisation to avoid residual phyto-toxic effects. In addition, the ‘repressive’ action (e.g. the power to lower the frequency of some root diseases as Phytophtora, Pytium, etc.) is appreciated.

Several analytical measurements and trials have shown the suitability of composted products in such field of use.

In general the quantity of stable compost in a blend with peat and other organic and mineral materials (i.e. barks, sands, perlite, pumice, clay) ranges from 30 to 50 % in volume. If the blend is meant for the cultivation plants such as azalea, heather, rhododendron that need a very low pH value, the amount of compost in the blend is to be reduced to 10-30 %, as it is neutral to slightly alkaline.

The two negative potential hindrances that could prevent the compost from becoming a basic component of the substrates in the nursery sector are:

1. The residual phyto-toxicity of fresh composts that may negatively affect roots and plant physiology. Maturity of compost is definitely one of the most important request to promote its use as a substrate, but often this request is not accomplished.
2. The salinity, that must not exceed 1500-2000m S cm^-1. The green waste compost is well below this limit values while compost made of mixtures with high percentages of food waste tends to be above (2000-5000 m S cm^-1). In this second case, the food waste compost has to be mixed with peat or green waste compost.

Table 3 summarises potential markets, restrictions to the use and prices of the composted products according to specific sector requirements.

Table 3. Potential market, restriction of use and prices of the composting products

(*) the prices are referred to compost sold loose
(**) to private citizens the compost is sold by retail (bagged) and it is usually mixed to others materials

The price of compost in the different sectors derives from the average of compost prices surveyed in some European countries. A part the land reclamation, the least price is that of compost for field crops (e.g. cereal and corn growing) even though, this has to be foreseen as the main sector for future compost utilisation. The highest price is that of compost for nursery and gardening. The higher incomes of such sectors, on the other hand, claim for a sharp evaluation of technical characteristics of compost such as stability (measured through plant growing tests, the respirometric index and/or the Rottegrad index), stock homogeneity, phyto-toxicity, physical and hydrological parameters.

5. MARKETING AND PRODUCTION

The overall of food and green waste compost production within the European Union is some 5,000,000 t y^-1 approx. Germany, Austria and The Netherlands are the leading countries in the compost production as well as in the enhancement of strategies to promote it.

Table 4 shows the compost production in Countries. It can be seen that also Denmark and Belgium (Flanders) produce and market relevant amounts of compost; while, in Sweden, Luxembourg, Finland, France, Italy and United Kingdom the production and commercialisation of compost is increasing year by year. In the last group of countries (Greece, Ireland, Spain, Portugal) compost production is not yet relevant. This is to be seen as a paradox as, in fact, because of weather and cropping conditions all the soils of the Mediterranean countries, suffer from a structural lack of organic matter.

Table 4 Compost production in the European Union

(*) 0.55 t/ m³
In Italy the compost produced for the time being is mainly given, with fairly good incomes, to the hobby gardening sector. It is easy to forecast this sector to be saturated in next years with the rise of compost production Therefore the compost producers should find new markets able to buy large amounts of compost even though with less incomes. One of these potential market is landscaping which is naturally inclined to compost use. In this field, some positive actions have been undertaken to stimulate and promote the use of compost in the management of public green areas and parks; an example is the introduction in some tenders for the management of public resorts of the compulsory use of quality compost.

6. COMPOST QUALITY APPROACH IN THE EUROPEAN UNION

The quality labels have the double function to both protect the consumer’s interests and to promote effective instrument for compost producers to improve marketing features of their product. In some cases, to join a Quality Assessment Association means to lighten law liabilities (e.g. the recently issued German law has special provisions for Quality Assessment). In some European countries, the registration to an association of compost producers does not imply automatically the right of using the quality label. As an example, the procedure followed by the German Federal Organisation for Compost Quality Control BGK and by the Flemish Organisation VLACO for the promotion and marketing of bio compost and green compost is divided into the following steps: it starts from a recognition phase than by an application phase and finally, after two years, comes the granting of the label. In both cases also public bodies are involved in the quality label issuing procedures: in Germany, the BGK, recognised by the RAL Institute, has the task of checking the composting plants, in Belgium, the OVAM, body of the Flemish Ministry of the Environment, is part of the VLACO’s structure since its members are responsible for the ordinary management of the label.

In Italy, the Consorzio Italiano Compostatori (C.I.C.) has been founded in order to gather operators and possibly provide them with labelling procedures similar to the German Bundesguetemeinshaft and to promote, diffuse and improve the valorisation of the composted products and the technologies for compost production.

One more chance is provided trough the use of Ecolabel for soil improvers in the gardening sector whose assignment criteria have been defined in the EU Decision 7/4/98.

Interviews of some compost producers have showed that, so far, Ecolabel for compost has not been successfully applied within the EU Member States due to many reasons such as the little knowledge of the Ecolabel itself, the low added value provided by the use of the label and the risk of further checks of the compost stocks.

Table 5 shows the heavy metal limits for compost stated by the different regulations and Quality Label Assessment Associations.

The comparison highlights a wide heterogeneity among the values (e.g. the Zinc according to the French Fertiliser Law is allowed to be 1500 mg kg^-1 while in The Netherlands is 75 mg kg^-1). In some nations such as Austria, Germany and The Netherlands compost is divided into different quality classes; this allows to market also composts that, being equal as agronomic properties, have low environmental performances.

It is important to stress also that the average heavy metal content of food waste compost is higher than that of yard waste compost (as for salinity § 4.2); this variability should be taken into consideration by the legislators in the European Directive on Composting that should be issued soon.

Country	Regulation	Cd	Crtot.	Cr VI	Cu	Hg	Ni	Pb	Zn	As	Label
European Union	EEC 488/98 Ecolabel	1.0	100		100	1.0	50	100	300	10
European Union	EEC 2092/91-1488/97 Organic farming	0.7	70	-	70	0.4	25	45	200		/
Austria	ÖN S2200 1993 Class I Class II Class III Federal Draft: farming land remediation	0.7 1.0 4.0   1.0 3.0	70 70 150   70 250	- - -   - -	70 100 400   150 500	0.7 1.0 4.0   0.7 3.0	42 60 100   60 100	70 150 500   150 250	210 400 1000   500 1200	- - -   - -
Belgium	Farming Parks and Gardening Vlaco (Flanders only)	5.0 5.0 1.5	50 200 70	- - -	100 500 90	5.0 5.0 1.0	50 100 20	600 1000 120	1000 1500 300	- - -
France	Fertilizer law	1.5	300	-	600	1.0	100	100	1500	-	/
Denmark	Before 01-06-2000 After 01-06-2000	0.8 0.4	- -	- -	- -	0.8 0.8	30 30	120 120	- -	- -	/
Germany	Federal BioAbfV (1998) classe I classe II	1.0 1.5	70 100	- -	70 100	0.7 1.0	35 50	100 150	300 400	- -
Italy	Fertilizer law (3/98) Green and biocompost	1.5	-	0.5	150	1.5	50	140	500	-
Luxemburg	Draft (as RAL)	1.5	100	-	100	1.0	50	150	400	-
The Netherlands	Clean Compost Very clean Compost	1.0 0.7	50 50	- -	60 25	0.3 0.2	20 10	100 65	200 75	15 5.0
Spain	draft amendment	10	400	0	450	7	120	300	1100	-	/
United Kingdom	OWCA	10	1000	-	400	2	100	250	1000	-	/

7. PECULIARITY OF THE MEDITERRANEAN COUNTRIES

Best valorisation of the composted products is accomplished through marketing strategies suitable to the peculiar reality of the single Countries. In fact, in Germany priority is given to the protection of wet lands, while in Mediterranean countries the problem is to face the degradation of shores, coastal areas and soils. Moreover, the Mediterranean countries are potentially affected by desertification threat because of soil depletion of organic matter. This depletion causes, in turn, other damages such as erosion, soil compacting and saltiness. Compost has the suitable characteristics to be helpful in fighting these phenomena. A suitable tool to promote organic recovery would be a planning to define criteria and quantity of organic matter to be supplied. Such a ‘Plan for organic fertility in the soils’ should be aimed at the identification of potential needs (risk areas, degradation phenomena) and supplies (availability of source separated organic waste, strategies to increase it).

8. DISCUSSION AND CONCLUSIONS
   The evaluation of the agronomic properties of the composted products does not underestimate or exclude the use of other traditional bio-masses like manure for open fields and peaty potting mix for the nursery sector. In fact, from a technical point of view, composts, even though with differences due to the initial feedstock, have intermediate characteristics between manure (compost has a minor content of nutrients) and peaty materials (higher pH value and salinity of compost). Therefore, in general, composts cannot be considered as a material ‘ready to use’ (the only two exceptions are hobby gardening and the direct application as soil improver in the field) but they can be seen as half-processed product that need further improvements (e.g. addition of nutrients, pH adjustment) to meet commercial requirements. Actually, this applies also to those products, that can be substituted by the composted products, and have a sound market and a technical history behind them.

In order to increase their added value, compost need to be ‘modified’ to obtain specific features for different sectors.

Summarising, compost could be sold in two different ways:

• sale of loose product
• sale of specific products with added value through addition of nutrients and minerals, adjustments of pH and physical properties, physical-chemical treatments (pellet, granular compost).

Two opportunities can be pointed out to get higher prices:

1. production of growing media certified with quality labels. As an example, in some countries of central Europe, specific quality labels have been created for peat-free (compost-based) growing media. These products have good agronomic performances and are perceived by the consumers as environmentally friends thanks to the reduced peat extraction from wet lands.
2. Investigation of alternative options to the nursery sector. A possible opportunity is the production of compost in pellet or granular to be used as organic or organic-mineral fertilisers in field crops or in landscaping. The latter, whose growth has showed to be relevant in recent years, is the sector with best marketing opportunities in the short term.

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