Dumpster Diving: Risks and Reasons

Why do we dumpster dive, why is there so much food in the bins and how do we not get sick? This post explores the risks we face and how we manage them, the reasons things are thrown out and why we dumpster dive.

Food Waste in Context

Food waste is immense and Australians are among the worst offenders, throwing out almost 180kg per person each year from retail, restaurants and homes as seen below. A similar amount of food is wasted before even getting to retail.

About one third of all food produced globally is discarded.¹ In high-income countries, most waste happens at retail and household levels, while cosmetic standards also contribute to on-farm waste. Even greater wastes arise from animal agriculture and bio-fuels. Together these consume more than half of the cereals produced worldwide and 80% of those used in Australia as shown below.

It takes 38kg of plant protein to produce 1kg of beef protein with the rest being excreted to as a nutrient burden on waterways and other natural systems. Chicken is slightly less wasteful, requiring 4.8kg per kilogram. I will discuss biofuel in a future post.

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Reducing Waste

The most effective path to reduce food waste is to reduce consumption of animals and animal products. This is in-fact a necessary change to have any chance at a sustainable existence within planetary limits.³ It also come with myriad other benefits as previously explored. Reducing waste at home and while dining out are also critical. This involves:

• buying only the food you will eat in appropriate quantities
• increasing the ratio of food prepared at home vs dining out
• buying “second choice” produce and almost expired items
• avoiding pre-cut salads and other reduced-life convenience items
• making the most of what you already have, including left-overs
• sharing accidental excess with neighbours
• trusting your senses over nominal dates on purchased items
• choosing shelf-stable options and rotating through them

Dumpster diving is not essential for one-planet-living, and not even a significant option on a broad scale, since only about 2 to 5% of food is wasted at the retail stage.

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Why Dumpster Dive?

Emelie and I dumpster dive to reduce that waste and save money, enabling us to give more to high impact charities. A year of diving saves us about $7,000 AUD, which buys nutritional supplements for about 5,000 children. But there are a quite a few reasons people might forage in an urban environment:

• To reduce waste (and land-fill emissions)
• To save money
• For resale (not for food – be cautious with other items)
• For the thrill
• For community and curiosity
• Out of necessity

Each of the motivations will come with a different tolerance for risk. While all sorts of things are thrown out, this post focuses on food.

More people may find themselves tempted to explore dumpster diving over the coming months as energy and fertiliser shortages drive up the price of food. Anyone considering diving should be particularly mindful of others who may depend on the activity for their survival. Negative attention will result in locked bins. We are neither condemning nor endorsing dumpster diving, just sharing our experience.

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Findings from the Field

Where and When

Some stores are more reliable and accessible than others. Urban bins often contain usable food mainly on weekends and public holidays because the food rescue charities are understaffed on weekends. Regional stores may discard stock throughout the week. Often the bins are in the loading dock or off to one side. We do not enter locked areas.

Best timing tends to be about one hour after opening or one hour before closing on busy weekend days. If we can get to freshly filled bins it reduces the time-above-temperature risk, though there is no guarantee something wasn’t left warm and then chilled prior to disposal.

We try to go together for safety and confidence. We know we’re doing the right thing, but it’s still nerve-wracking at times. Confidence has built with time. Diverting waste is the right thing to do. Leaving waste to rot to methane while clearing land to produce ever more is not.

Hygiene

We look at the best-before dates on the products as we dig. The stores buffer waste internally before disposal, so older items may sit on top of the outdoor bin because they were in the bottom of the indoor bin.

Water for hand washing and spare bags help contain any mess or loose items such as eggs. We try to leave everything cleaner than we found it. Other divers and staff are affected by our behaviour.

Once home we wash everything thoroughly and take another look in bright light and sniff in neutral air. Then we photograph what we collect and share surplus with our neighbours. Even collecting with our bikes it is easy to gather more than we need. We are very transparent about the origins of the food and potential risks. All of our neighbours have been quite receptive.

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Why Food Gets Thrown Out

Food is discarded at the retail stage for several reasons and much of it is still fine for consumption:

• Out of date (usually fine)
• Cosmetic damage (fine)
• Overstocking (fine)
• Packaging damage (usually fine)
• Recalls (may be fine, see below)
• Pest damage (may be fine, eg. weavils)
• Temperature control breaches (questionable)
• Actually spoiled or unuseable (often one item in a package eg. fruit or eggs)

Cold food is not automatically safe. Several supermarket employees have reported a standard practice of putting any spoiled food in cold storage prior to disposal to minimise smell. In which case it may already have experienced bacterial growth and toxin formation. The same checks apply whether it feels cold or warm. Food that looks perfectly fine should be treated with extra caution. For this reason, we are more comfortable taking meat and dairy products that have visible packaging damage or are past date, as these are less likely to have been left warm. That risk still remains.

Recalls & Specials

Any time one thing shows up in substantial volume, there’s a reasonable chance it’s due to a recall. You can usually search the product details online and find the reason. This could be.

• Physical contamination (metal, plastic, rubber or glass)
• Biological contamination (salmonella, listeria or e. coli)
• Mislabelling (eg. unreported allergens)

How you approach each of these depends on your risk tolerance. Not every product will be contaminated and even contaminated products may be unpleasant rather than hazardous. I would steer clear of potential glass contamination and only collect the bio-contaminant recalls for cooking (if reported as one of the cultures that may be heat-neutralised). The other reason for one-time abundance is holiday specials.

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Contamination

As far as I understand it, healthy adults will tolerate most foodborne infections well. They may experience discomfort for several days if unlucky. Anyone with compromised immunity, pregnancy, mold allergies or limited access to water or hygiene facilities should take extra care. Severe complications are rare but people do die every year due to food-borne illness. We have been eating almost entirely dumpster-derived meals for about six months and so far have no sickness. The past, however, is no guarantee of the future.

The main biological hazards from consuming rescued food fall into two categories:

Living pathogens

• Managed by sorting, washing, trimming, peeling, and cooking
• Typically cause short-term gastrointestinal illness if still present

Pre-formed toxins

• Not all neutralised by normal cooking
• Often associated with warm, moist, protein-rich foods
• Cause rapid vomiting or diarrhoea

Visual and sensory checks remain important tools:

• Strong sour or putrid smell suggests advanced bacterial decay
• Sliminess on leafy greens indicates heavy microbial growth
• Bulging packaging indicates advanced decay
• Discolouration suggest drying or oxidation from failed packaging
• Bulging cans signal anaerobic gas production
• Musty odour in nuts or flour suggests mold

Our ancestors and even our grandparents relied on their senses to keep them mostly safe from food-borne illness. On the other hand modern tolerance for risk is vastly lower, since eliminating most non-dietary hazards. It is worth repeating that dangerous levels of some pathogens may be present without any obvious signs.

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Bad-ass Bacteria

The most common sources of biological contamination, including e. coli, listeria, campylobacter, salmonella and vibrio, are effectively managed by adequate cooking.⁴⁵⁶⁷⁸ This does not apply to the pre-formed toxins from bacillus cereus or staphylococcus aureus which are heat stable. Sufficient heat kills bacteria, but does not reliably neutralise certain toxins.

The spores of clostridium botulinum are also not destroyed by cooking. This anaerobic bacteria can continue to multiply in sealed containers after heat treatment, provided the pH is greater than 4.6. They produce the deadly botulinum toxin. Unlike the b. cereus and staph toxins, the botulinum toxin is destroyed by adequate heat. The World Health Organisation recommends exposure to 85°C for five minutes.⁹ Thus any home-canned food should be thoroughly reheated prior to serving, particularly if it was from suspect origins such as a dumpster.

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Favourable Fermentation

Fruit and acidic or sugary products are sometimes fermented with yeasts or lactobacillus culture, producing alcohol and acid.¹⁰ Early fermentation is typically low risk and may even improve digestibility.¹¹ We have enjoyed fruit juices that have commenced fermentation, producing a pleasantly sour and fizzy cider. I have also had several coleslaw salads that had commenced their journey to saurkraut. Advanced wet rot is a different story, easily distinguished by a putrid smell.

When Emelie and I go diving, if we can smell the bin before we open the lid, or immediately find maggots we know we’re too late for fresh products. We may still forage for shelf stable items with intact packaging that can be washed off.

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Risk Hierarchy for a Healthy Adult

Discarded meat or soggy produce scraped from the soup at the bottom of the bin is not for everyone. But there are range of lower risk options.

Lower concern categories:

• Just expired bread and pantry items
• Mislabelled recalls
• Cosmetically damaged packaging
• Whole fruit with intact skin
• Hard cheese with or without trimmable mold

Moderate concern:

• Leafy greens that can be washed or cooked
• Sour milk and fresh cheese
• Bottled juices
• Soft fruits with porous packaging such as raspberries
• Soft cheeses
• Icecream and similar freezer items that have thawed but remain cold
• Meat or non-scombroid fish that will be thoroughly cooked¹²

Higher concern:

• Slimy or smelly meat or fish
• Tuna, mackeral and other scombroid fish
• Cream filled items, unless they will be recooked
• Cooked rice or pasta
• Mixed protein salads
• Thawed frozen meals
• Bulging canned goods

This is a general guideline and not intended as advice. Readers are encouraged to do their own research. Links are provided below.

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Risks and Remediations

Food	Spoilage Mode	Culture / Hazard	Signs	Complications	Remediation	Residual Risk13
Fruit / juice	Fermentation	Wild yeasts (ethanol)	Alcohol smell, bubbling	Sour taste; mild GI upset	Trim damaged areas	Negligible
Fresh fruit (firm)	Surface mold	Penicillium, Aspergillus	Localized fuzz	Mild GI upset; mycotoxin liver damage	Trim ≥2 cm around spot	Very low
Fresh fruit	Advanced soft rot	Mixed bacteria	Wet collapse, foul odor	Vomiting; diarrhea	Discard	Moderate
Leafy greens	Surface contamination	Salmonella, E. coli	Often none	Diarrhea; cramps; dehydration	Vigorous washing; cooking	Low if washed; Very low if cooked
Leafy greens, potatoes	Spoilage	Listeria monocytogenes	Often none	Flu-like illness; rare invasive infection	Thorough cooking (≥85°C)	Very low
Root vegetables	Surface mold	Environmental molds	Fuzz on skin	Usually none; mild GI upset possible	Peeling; cooking	Negligible
Cooked rice	Toxin accumulation	Bacillus cereus toxin	Often none; Possible sourness	Sudden intense vomiting; diarrhea	Discard (cooking ineffective)	High
Mixed cooked dishes	Toxin accumulation	Staphylococcus aureus	Often none	Rapid vomiting; severe nausea	Discard (cooking ineffective)	High
Raw meat (whole cuts)	Enteric bacteria / campylobacter	Salmonella, Campylobacter jejuni	No reliable sign	Diarrhea; fever; rare bacteremia	Thorough cooking (≥70°C core)	Low
Raw meat (ground)	Shiga toxin bacteria	E. coli	No sign	Bloody diarrhea; rare kidney failure	Thorough cooking (≥70°C core)	Low
Raw meat	Mixed growth	Various incl. toxin producers	Sour smell, slime, swollen package	Vomiting; diarrhea; possible systemic illness	Discard	High
Deli meat	Listeria	Listeria monocytogenes	Slimy surface	Mild illness; rare invasive infection	Wash & reheat thoroughly (≥85°C)	Low
Fish	Protein breakdown	Shewanella putrefaciens, Pseudomonas fluorescens	Sharp fishy smell, sometimes slime	Unpleasant taste; possible mild GI upset	Cook if not offended by taste	Low (strong taste remains)
Fish, esp. tuna & mackeral > 25°C for > 6h	Histamine formation	Morganella morganii	Slight pepper or metallic taste	Rapid onset flushing, headache, rash; vomiting	Cooking not effective.Discard if detected	High
Bread	Surface mold	Aspergillus, Penicillium	Visible mold	Mild GI upset; mycotoxin liver damage	Discard contaminated portions	Very low
Bread	Rope spoilage	Bacillus subtilis	Sticky crumb	Nausea; unpleasant texture	Discard	Moderate
Baked goods (cream-filled)	Staph toxin	Staph enterotoxin	Often none	Rapid onset vomiting	Discard	High
Hard cheese	Surface mold	Penicillium spp.	Local mold	Usually none	Trim ≥2 cm margin	Negligible
Soft cheese	Mold infiltration	Various molds	Mold beyond rind	GI upset; toxin exposure	Discard	Moderate
Milk (slightly sour)	Lactic fermentation	Lactobacillus	Sour smell	Mild GI symptoms	Use in moderation	Negligible
Milk (kept warm)	Pathogen growth	Salmonella, Listeria	Often none	Diarrhea; fever	Thorough cooking (≥85°C core)	Very low
Eggs	Salmonella	Salmonella enterica	No sign	Diarrhea; fever	Cook fully (≥70°C)	Very low
Nuts	Rancidity	Lipid oxidation	Bitter taste	Unpleasant flavour	Consume if tolerable	None
Nuts	Mold	Aspergillus flavus (aflatoxin)	Musty smell	Chronic liver toxicity (repeated exposure)	Discard moldy nuts	Very low
Grains / flour (dry)	Insects	Weevils	Visible insects	None beyond appearance & texture	Freeze to kill insects	None
Grains / flour (wet)	Mold growth	Various molds	Clumping, musty	GI upset; possible toxin exposure	Discard moldy portions	Very low
Canned goods (minor dent)	Cosmetic damage	—	Side dent only	None	Safe if seam intact	None
Canned goods (bulging)	Botulinum toxin	Clostridium botulinum toxin	Bulge, hiss	Progressive paralysis; respiratory failure	Discard unopened. Reheat thoroughly (5 mins ≥85°C) if apocalyptically desparate	Moderate

Closing Thoughts

Our dumpster diving videos on Facebook, Instagram & TikTok have got a lot of attention, including from mainstream media. It would be easy to get carried away by the excitement and attention, but it’s important to remember this is a small part of a much bigger picture.

As a society Australia and comparable nations are destroying the earth many times faster than it can regenerate and food is the biggest factor. We all need to be asking: why is edible food being discarded while land is cleared for agriculture and grain is fed to livestock and machines, instead of the 400 million undernourished people of our planet.

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References

1. Food and Agriculture Organization of the United Nations (2011) Global food losses and food waste https://openknowledge.fao.org/handle/20.500.14283/i2697e ↩︎
2. A Shepon et al. (2016) Energy and protein feed-to-food conversion efficiencies in the US and potential food security gains from dietary changes, Environ. Res. Lett. 11, 105002, https://iopscience.iop.org/article/10.1088/1748-9326/11/10/105002 ↩︎
3. Rabès, et al. (2020) Greenhouse gas emissions, energy demand and land use associated with omnivorous, pesco-vegetarian, vegetarian, and vegan diets accounting for farming practices,
   Sustainable Production and Consumption, 22, https://doi.org/10.1016/j.spc.2020.02.010 ↩︎
4. World Health Organisation (2018) E. Coli Fact Sheet, https://www.who.int/news-room/fact-sheets/detail/e-coli ↩︎
5. World Health Organisation (2018) Salmonella Fact Sheet https://www.who.int/news-room/fact-sheets/detail/salmonella-(non-typhoidal) ↩︎
6. World Health Organisation (2020) Campylobacter Fact Sheet https://www.who.int/news-room/fact-sheets/detail/campylobacter ↩︎
7. Food and Agriculture Organization of the United Nations (2007) CAC/GL 61 – 2007: Guidelines on the application of general principles of food hygiene to the control of listeria monocytogenes in foods, search https://www.fao.org/fao-who-codexalimentarius/codex-texts/guidelines/en/ ↩︎
8. Chintagari, S., Hazard, N., Edwards, G., Jadeja, R., & Janes, M. (2017). Risks Associated with Fish and Seafood. Microbiology spectrum, 5(1), 10.1128/microbiolspec.pfs-0013-2016. https://doi.org/10.1128/microbiolspec.PFS-0013-2016 ↩︎
9. World Health Organisation (2023) Botulism Fact Sheet, https://www.who.int/news-room/fact-sheets/detail/botulism ↩︎
10. Oluwadara A. et. al. (2022) Microbial spoilage of vegetables, fruits and cereals,
    Applied Food Research, 2(1),100122 https://doi.org/10.1016/j.afres.2022.100122 ↩︎
11. Knez, E., Kadac-Czapska, K., & Grembecka, M. (2023). Effect of Fermentation on the Nutritional Quality of the Selected Vegetables and Legumes and Their Health Effects. Life (Basel, Switzerland), 13(3), 655. https://doi.org/10.3390/life13030655 ↩︎
12. Food and Agriculture Organization of the United Nations (2012) Public Health Risks of Histamine and other
    Biogenic Amines from Fish and Fishery Products, https://iris.who.int/server/api/core/bitstreams/188b9afe-c797-4d2b-a8d2-f61efd7d7c84/content ↩︎ ↩︎
13. This is our inexpert interpretation of the fact sheets above and assessed against our personal risk tolerance. It is not intended as advice. ↩︎