Ample evidence is available in the qualified literature on the diversion potential of biodegradables. Composting, digestion with or without methane capture, reuse as animal feed and even incineration are well-documented technologies. Although the technical aspects of diversion are well attended to, diversion rates achieved in practice are low. The research described here studies the life cycle of basic food items in order to discover the reasons for the low landfill diversion rates of this material. The result points to management failures at key points of the cycle as basic obstacles to higher diversion rates. 

The study looks into commercialization procedures of fruit and vegetables before consumption, into consumption proper and into after-consumption disposal procedures for food scraps in the Brazilian context. Results are surprising. Before consumption, the rate of lost fruit and vegetables stands at 16 weight percent of the total quantity commercialized. During consumption by residents, the waste rate of food amounts to 9 weight percent of all collected household garbage. In the after-consumption lap of the cycle, biodegradables represent 72 weight percent of all household garbage collected by official means in a typical Brazilian town. 

These numbers produced by the study are impressive and clearly identify landfill diversion of biodegradables as a management problem. The authors faced the challenge and experimented with original proactive administrative procedures which led to more surprising results. The occurrence of wasted fruit and vegetables at the wholesaler and retailer levels is identified. Remedies are proposed and tested to reduce the waste rate by at least 50%. In the after-consumption lap, the notion of divided garbage collection is developed and applied to test communities. It is shown that biodegradables may be collected separately from the rest of household waste. This results in a diversion potential of 100% for biodegradables alone and 77 weight percent for all collected household waste. Models are presented that show the material flow in the life cycle of biodegradables with emphasis on management actions. The study produces a formal proposal to municipal administrations to avoid the need for biodegradable landfill through implementation of divided collection and composting or digestion of all organic material in household waste.
Key words: material flow analysis, integrated bio-systems, food commercialization losses, household waste, divided collection, landfill diversion.
 

Introduction

The term biodegradables in this context refers to the wide variety of perishable organic matter present in municipal solid waste (MSW), all of which decomposes under normal atmospheric conditions. Out of this large spectrum of matter, the present research chose to cope with waste derived from production, commercialization and consumption of fruits and vegetables. At first sight, landfilling this material may seem logical, as it would close its life cycle by returning it to nature. Necessary conditions for this procedure would be reasonable purity of the organic material at the tip and completion of the biological decomposition reactions before tipping. In present day practice, a landfill does not close any life cycles. It leaves all of them open. Landfills are accepted to be permanent depositories of mixed waste, carefully isolated from their environment by appropriate impermeable layers at the bottom and methane scavenging vegetation at the top. They perfectly fit the description of the parallel planet defined earlier by Fehr (1999a), as they ostensibly represent the gap in the material balance of all matter derived from earthly resources. A commendable attempt is usually made to integrate closed landfills into the landscape and thus return the terrain to civic uses. Their contents, however, do not return to their original state in nature in the foreseeable future. Photograph 1 shows such a new landscape hiding the parallel planet underneath the cover soil.

Consequently, seen from an ecological point of view, which advocates the closure of life cycles, landfills are undesirable solutions to the problem of waste disposal. The philosophy of landfill diversion is rapidly expanding its influence. Its basic premise is to discover and put into practice processes, technologies and management methods that help close the material balance of the environment without resorting to the parallel planet.

The present study adheres to this modern diversion philosophy and experiments with specific management tools with the intention to divert biodegradables from landfills. Why is the emphasis placed on management tools and on biodegradable matter? The answer is that both offer an excellent perspective to create strong impacts on diversion rates. Existing technologies by themselves have not been able to significantly raise diversion rates of biodegradables in spite of the impressive apparent potential, and biodegradables in Brazil typically represent 70 weight percent of MSW. The available and well seasoned technologies for treating biodegradable waste components are composting (Pereira Neto 1989, Green 1999, DSWA 1999), accelerated anaerobic digestion (MWPF 1996), landfilling with methane capture for power generation (Ville de Montréal 1992, Schoen et al 1999, Fehr 1999c), landfilling without methane collection (Read 1997, Fehr 1999b) and mixed waste incineration (Fehr 1992, Remmen 1998, Stöhr et al 1998). The first two of these technologies produce compost and therefore may be considered means of closing the material balance and the life cycle. For the present study, they appeared to be logical targets. It remained to bridge the gap between the waste producers, the households, and the waste consumers, the operators of composting facilities. This gap is of an administrative nature. Existing mixed waste collection and separation technologies do not deliver adequate raw material to the composting facilities to make them successful enterprises. 

Any company or organization specializing in composting or accelerated anaerobic digestion, of necessity, judges the success of these operations by economic criteria. As a result, an isolated biological and economic micro-system is created, which is trapped within the battery limits of the specific technology or process. The raw material of this bio-system is the mixed waste received at the tip gate. Its product is the compost sold to interested parties at going market prices. If no added value is achievable with this transformation, obviously nobody will invest in the system, and the biodegradables go to the tip. What is the challenge? Look at this micro-system as but a tiny component of an integrated bio-system, which comprises all parts of the food life cycle, and apply the economic analysis to this integrated system. Suddenly, strategic considerations such as opportunity costs of landfill terrain and contents enter into the calculation. The economic analysis trespasses the battery limits of the composting plant and assumes national proportions. The authors have not encountered this type of macroscopic assessment with corresponding practical solutions in the qualified literature. All landfill facilities visited and studied through publications are trapped in the battery limit approach of management strategies for biodegradables. Landfill diversion remains low simply because it has never been a specific management priority at regional or national levels.

In this context, the specific objectives of this study were the following. Observe the life cycle of basic fruit and vegetable food items in order to discover where and at what rates biodegradable waste is produced. Devise management methods for closing the waste processing gap between households and composters. Develop and test a management model acceptable to municipal administrations. The target based on previous research was a total landfill diversion of MSW in the order of 80% with all its economic implications at regional levels. The life cycle study afforded some insight into the material flow between the following specific fruit and vegetable bio-systems: soil preparation and food production, commercialization with waste generation, consumption with waste generation, waste disposal, reintegration into soil preparation, and landfill bio-systems of the parallel planet.
 

The observed life cycle of fruits and vegetables

 Fruits and vegetables were chosen as a sample commodity of biodegradable food in order to study the generation of waste during the life cycle and the possibilities for its diversion from landfills. The wording is critical in this treatment. Scraps refer to customary remains after consumption: the parts that are not eatable. An example is a banana peel. Loss refers to entire food items that do not serve their purpose: they are thrown away without being considered for consumption, for whatever reasons there may be. An example is an entire banana found in the garbage. The words waste or biodegradables are used to address the sum of scraps and losses. For convenience of analysis and data presentation, the life cycle was divided into laps G for growing, M for marketing, C for consumption and D for disposal. Lap G runs from soil preparation to harvesting. Lap M runs from the farm gate to the retail sale. Lap C runs from the retail purchase to the garbage can, and lap D runs from the garbage can to the landfill.
 
 

Data were collected at the following key points of the life cycle: commercialization procedures prior to consumption (M), consumption proper (C) and after-consumption disposal of residues (D). The study is based on the hypothesis that all fruit and vegetable items are in perfect conditions for consumption upon leaving the farm. As a consequence, no waste data were collected for lap G. In the typical Brazilian context, farmers screen their produce at home and then transport it to a wholesale market at the outskirts of the nearest city. At this market, they may sell to wholesalers or to retailers, according to their convenience. For logistical reasons, the study is limited to this distribution model of produce which is the only one visible. A farmer who bypasses the market and delivers the produce directly to an individual customer, or a wholesaler or retailer who imports produce without moving it through the wholesale market, are outside the physical reach of this study. Some wholesalers have reasonable infrastructure to maintain stocks for delayed commercialization, either at the wholesale market or at their private property. Others do not. For them, speed of commercialization is a critical parameter. They need a fixed net of retailer customers to guarantee the continuous flow of the merchandise. Their negotiating power is limited. The retailers present at the market take their purchases directly to their respective sales outlets in town, which may be street markets, restaurants, fruit and vegetable stores, general food stores or supermarkets. In all cases, the marketing lap of the life cycle of fruits and vegetables begins at the farm gate and ends when the consumer acquires the products at the retail outlets. Specific data on commodity turnover and waste generation were collected  at the wholesale market with farmers and wholesalers, and at the retailer level with fruit and vegetable stores, street market traders and supermarkets. 

The section of the life cycle termed consumption (C) in this study comprises the time and the handling steps from the moment when the food is purchased at the retailer’s to the moment when the remains appear at the side walk for garbage collection. This section was diagnosed by way of sorting and analysis of garbage left at the side walk by dwellers of apartment buildings. 

Finally, the portion of the life cycle concerned with after-consumption disposal (D) begins at the side walk and terminates at the landfill. According to the theory of the parallel planets mentioned earlier, all tipped matter leaves the planet Earth and forms the parallel planet Trash. The life cycle remains open. The only way to close it is to compost the biodegradable waste and return the compost to the farm. This study produced data on the rate at which biodegradable matter changes planets. The extrapolations are somewhat frightening.  Figure 1 shows the basic stops of fruits and vegetables in their life cycle for the Brazilian context under study.
 

Data collection and results at the wholesale level

 For the marketing lap of the life cycle, the gathered data were expected to answer question 1: What fraction of fruits and vegetables produced on the farms and offered for commercialization actually reach the final consumer? As no consumption occurs in this lap, all waste derives from losses. There are no scraps. All supply vehicles arriving at the wholesale market are weighed, such that the quantity of produce offered for commercialization is known. Table 1 shows data for the specific market subject of this study. It serves a municipality with 440000 inhabitants and receives produce from 1283 registered farmers and importers.
 

Outgoing vehicles are not controlled, such that no official data exist on the destination of the produce supplied to the market. The present research produced the following original data on this topic. Quantitative information was obtained from the work with wholesalers at the market. Through daily follow-up of purchases and sales at 3 sample companies, and scale-up to the 58 companies engaged in wholesale, data collected from August 1998 to March 1999 showed that 4.32% of produce purchased by wholesalers deteriorates on their property and is thrown away. In addition, there exists a section which receives donations in the form of fruits and vegetables that do not find buyers but are still eatable at a consumer's discretion. The quantity of donations during December 1998 was measured to be 302.6 tons.  As no revenue is derived from them, they are accounted for as waste in this study. Table 2 summarizes the situation defined by this research for the particular market analyzed. 
 

Data collection and results at the retail level

 Retailers take away from the wholesale market all produce not lost or donated. This amounts to 100 – 6.28 or 93.72% of turnover. Figure 1 lists the handling steps involved in retailing. The types of retailers analyzed here were street market traders, fruit and vegetable stores and supermarkets. The following numbers give an idea of the size of this universe. There are in this city 160 registered street market traders, 55 fruit and vegetable stores, 156 supermarkets of all sizes including ordinary food stores listed as supermarkets, apart from 87 restaurants which did not take part in this research. 

One typical street market trader was picked for analysis. Some of these traders complement the purchases at the wholesale market  with their own production. The main problem of the traders is to keep the produce fresh from the time of purchase or harvest to the moment of sale at one of the successive street market offerings. The trader under study did not have data either on his operational cost, or on the losses of produce. This research provided original data on this commercial sector. During the months of August and September 1998, this trader acquired 7.874 tons of produce of which 0.919 ton or 11.67% deteriorated  during the handling steps and was discarded. All tonnage in this report refers to metric tons.

The fruit and vegetable stores are businesses who specialize in retailing farm produce, which apart from fruits and vegetables may include poultry and milk derivatives. Two of these stores were chosen for analysis. Neither of them had any data on the quantity of losses, and both had only vague ideas about the causes of these losses. Once again, original data were generated on the effectiveness of this trade. Store B owned a cold chamber for intermediate storage of produce, store A did not. Both had suppliers other than the wholesale market to complement their purchases, but no account was kept on the exact quantities originating from each supplier. Table 3 shows the result of the measurements carried out in the two stores.
 

The last retail outlet to be studied was a supermarket of above average size. This type of business commercializes a great variety of products, of which fruits and vegetables represent only one department. Measurements were taken on two seasonally different occasions: November 1998 (rain season) and April 1999 (dry season). The result is shown on Table 4. 

On reaching the end of the marketing lap, a recapitulation of recorded data is in order. Due to the large and heterogeneous universe of commercial establishments in this lap, no attempt was made at closing the material balance of produce. The available data did not allow such an endeavor. The occurrence of material losses, however, may be estimated from the data collected. This was the prime objective of the study. The calculation on table 5 crudely summarizes the losses. The answer to question 1 is 83.41%.
 

Data collection and results in the consumption lap

 In this lap, the food items acquired by the consumer at the retailer’s pragmatically divide into 3 destinations. Part 1 is really consumed and exits the life cycle of fruits and vegetables to enter that of human energy, a different bio-system. Part 2 comprises the scraps, the uneatable portion of the fare which naturally and expectedly appear in the garbage. Part 3 is the loss: all items that bypass the kitchen and go from unpacking or storage straight to the waste basket. The research on this lap pretended to answer question 2: What fraction of purchased fruits and vegetables end up in part 3 and what fraction of household waste do parts 2 and 3 represent? To obtain the pertinent data, household garbage was collected and analyzed at selected points in town. An earlier study in this city (Fehr & Castro 1999) had determined the fraction of biodegradables in MSW as 72 weight percent. The present research was conducted in two apartment buildings that represented appropriate conditions for collecting the specific data sought. Dwellers were instructed to separate their garbage into two bags: biodegradables and inerts. This procedure was termed divided collection. It not only made analysis easier, but also opened up impressive perspectives for landfill diversion. Garbage was collected on various occasions until a steady state of division into the two bags had been reached, with 67% biodegradables and 33% inerts. Table 6 shows in material balance style the result of the last analysis of this series. The answer to question 2 is as follows. Lost fruits and vegetables represent 3.4% of household waste or 5.2% of biodegradables present in household waste. Biodegradable waste represents 66.6% of collected household waste from apartment buildings, which divides into 86.8% scraps and 13.2% losses. The first part of the question has no answer at this time, due to the discontinuity of measurements inside the household. To complete the data, it would be necessary to follow a family to the store and to the kitchen and weigh what they buy and what they throw away, in order to find what they consume by difference. Photograph 2 is offered to illustrate the identification of lost fruits and vegetables in the samples of household waste analyzed. 
 
 

The disposal lap

 The city under study operates a mixed waste processing facility (MWPF) which, according to information obtained from management, diverts an estimated 40% of collected waste from landfill. No specific data are available to confirm this statement. The effort of collecting this type of data was beyond the scope of this research.
 

Targeting landfill diversion

 From the data presented in the tables of results, it was possible to set a logical target for landfill diversion in this particular city. This exercise is original in the region, and possibly in other regions as well. In the marketing lap, table 5 indicates losses of 184849*0.1659=30666 t/y or 84 t/d of fruits and vegetables officially accounted for. They change planets without ever reaching the retail level. In the consumption lap, table 6 shows that for the apartment buildings studied, 66.6% of household waste is biodegradable. According to previous research (Fehr & Castro 1999), this number stands at 72% for the entire city. Apartment buildings represent a specific social level with above average living standard. This difference in composition is expected. In the following calculations concerning the city, the value of 72% will be used. In both laps, the key to diversion is proper management of people and technologies. As the marketing lap is concerned with manipulation of fresh produce, the elimination of waste is an unrealistic proposition. Conservatively and somewhat arbitrarily, based on personal observations in this lap, a target of 50% waste reduction was considered achievable. The disposal lap handles only waste originating from the consumption lap. No special care is required. Consequently, a landfill diversion of 100% for biodegradables was deemed a logical target. The official MSW collection in this city stands at 276 t/d (Fehr & Castro 1999). As a by-product of the waste analysis, table 6 also gives details on inert material. The recyclable portion of this does not need to be landfilled. The target for diversion is exposed in table 7.
 

Facing the management challenge

 With the diversion target known, it remained to find answers to question 3: What has been achieved, what needs to be done and how should it be done ? Obviously, this research was not expected to interfere with municipal administrations. The idea was to provide pertinent data, to develop management methods and to test their chances of success. What has been achieved is summarized in tables 5, 6 and 7. All numbers in these tables are the result of original research. None of them was known. For the first time data are now available on the losses of fruits and vegetables in the marketing and consumption laps of their life cycle. Also for the first time, a landfill diversion target has been quantitatively set based on real data. This represents a giant step towards modern waste management practices in any city or town still trapped in the era of unrestricted landfill, and there are many. 

What needed to be done was to find appropriate management procedures for both the marketing and the disposal lap. Work has been initiated with the following steps. Interviews with farmers have been conducted in order to pinpoint the factors leading to losses on loading and transportation. Convenient and inconvenient packaging material and hours of the day for transportation of produce have been identified. The numbers produced by this research have alerted wholesalers about the convenience of maintaining air conditioned storage areas and of hiring appropriate man power. The street market trader has been induced to exercise control over his cost structure and to optimize his purchasing schedule. The fruit and vegetable stores have become conscious of the causes of losses. They are inadequate purchasing schedules and poor practices of manipulating produce in the stores. At the supermarket, the most surprising result of this research was the promotion of the material balance to a higher level of priority. Acquisitions and sales of every fruit and vegetable item are now documented and compared in order to discover and quantify losses. 

 For the disposal lap, the model of divided waste collection has been developed and tested. Photographs 3 and 4 testify to the success of the tests. Photograph 3 shows the biodegradable portion of household waste being analyzed. It had been left at the curb side in separate bags and is practically ready for composting. Photograph 4 gives an idea of the quality of recyclable material contained in the inert portion of household waste derived from the divided collection operation. Specific theories behind and experiments with divided collection have been published elsewhere (Fehr & Calçado 1999). 
 

The steps outlined here indicate that a correct approach has been chosen to face the enormous management challenge of landfill diversion. The recent literature on this topic shows that the diversion problem is by no means local. Every country engages in finding the most appropriate method to cope with it. Examples have been found originating from Spain (GEDESMA 1998), East Asia (Taylor 1999) and Great Britain (Read 1999).
 

Discussion and perspective

 The objectives of this research have been fulfilled. The life cycle of basic fruit and vegetable food items has been defined and observed. Waste generation in this cycle has been quantified. The management method of divided collection has been developed and successfully tested. It closes the waste processing gap between households and composting facilities by supplying biodegradable raw material of excellent quality for composting. The model is considered useful for municipal administrations and may be implemented with modest investments. In addition to separating biodegradables, it separates recyclable inerts of excellent quality, too. Composting and recycling will thus attract the private initiative and alleviate the financial burden of the municipality. Obviously, the decision to accept and experiment with the model remains with public administrators. Admittedly, the effort to implement the model frightens administrators for the same reason it surprises engineers: It requires the ability to manage people. Once this fear of people is overcome, very rewarding and lasting results may be expected. 

As for the diversion target, the initial estimate was 80% of MSW. The work performed and the data collected came extremely close to confirming the prediction. The final number is 77%. As anticipated in the Introduction, the research provided interesting data on the material flow in the integrated bio-system of biodegradable food components. According to figure 1, the system is a closed cycle except for the exits of consumption and landfilling. It has been mentioned earlier that additional research is required to quantify the exit relating to consumption. The exit relating to landfilling has been determined as the sum of waste generated during the marketing and consumption laps of the life cycle. Numbers have been presented in tables 5 and 6 that quantify the flow rates and permit extrapolations. 
 The basic goal of this and related studies by the authors is to drastically reduce the rate at which biodegradables and other recyclable items change planets. For a city of 440000 people like the one studied here, in the era of unrestricted landfill, the transfer of matter from planet Earth to planet Trash is 276+84=360 t/d for MSW excluding construction and hospital trash. It is left as an arithmetic exercise for interested parties to extrapolate this number to their respective contexts. As an example close to home, the Brazilian population presently stands at 158 Million (IBGE 1997). All things considered, the philosophy of landfilling will inflate the Brazilian Trash planet at an approximate rate of 360*(158/0.44)=129300 t/d (metric tons per day). This is a fact. Any consideration on the continuous sustainability of life has to take this fact into account. If the present research succeeded in sounding the alert, it has been worthwhile.
 

Acknowledgements

 The authors thank the following Brazilian institutions for their support. The CAPES Foundation supplied a scholarship to M.d.R.Calçado. The CNPq Council supplied operational infrastructure to M.Fehr through grant 40.0040/96-4.

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