How to neutralize the stink of decomposed fish?

Question

Recently I discovered for myself an interesting way to easily produce home made plant fertilizer that is quite effective (tested myself on the plants). It's fish emulsion (so can be used also in a hydroponic system) - 1 part fish wastes(skin/bowels) to 2 parts water placed in an airtight container in a sunny spot for ca. 1-2 weeks. The problem - it stinks unbearably. Both - the gas that is produced during the decomposition and the liquid(/fats).

1. Is it possible to neutralize the stench somehow without loosing the fertilizing qualities of the emulsion? Especially of phosphorus.
   1.1 Ideally of both - the gas and the liquid. But at least of the liquid - as that is what is used actually and then continues to spread the smell after being added to the plants.
   1.2 Ideally it should be done using some usual household substances/wastes - maybe adding of lemon/orange peels along with the fish wastes? Or maybe ash/charcoals?

2. Ideally the resulting emulsion should be acidic as many plants like the pH range of 5 - 6.5 .

Answer 1

The difference between fish hydrolysate and synthetic NPK is the world of plant beneficial microbes you are culturing and adding to the soil. Have those microbes work for you to reduce odour during the ferment. Make a lactic acid bacteria (LAB) serum and add this along with molasses and biochar to the brew. The bacteria and molasses will kickstart fermentation to enzymatically break down the fish and it will inhibit the smell. You could also add commercially available plant probiotics and/or mychorrizal fungi to the brew to bolster the microbial diversity. Biochar is an effective way to reduce anaerobic odours such as hydrogen sulphide and methane. Put a lid on the bucket and install a water airlock so air can escape in a very slow and controlled way. The fertiliser could take 12 months or more to ferment so that the fish product has completely liquified. By the end of fermentation, the smell should be mild. When you apply the fertiliser you need to dilute it to at least 10 parts water, further reducing any odour. Because it will be heavily diluted, the pH shouldn’t matter too much unless it is extreme. If you need to correct the pH to become more neutral, add ascorbic acid to lower the pH, or dolomite lime to increase it, but only enough to neutralise the pH and no more. Do not add vinegar or lemon juice during brewing as it will kill microbes. Be sure to keep the product out of the sun as UV will also kill beneficial microbes.

Answer 2

Plants like fully decomposed (composted) organic materials just like humans prefer cooked food. The solution which you are preparing, is going to hurt the plants rather badly. For example, cow dung is a good organic fertilizer but fresh manure will burn the plants. Why don't you bury this fish waste in the ground or soil, mix it with old leaves and let it compost for 1-2 months? No smell should arise because soil bacteria and perhaps worms/insects will take care of it. Above all everything will be well covered with soil.

Do not add vinegar or lemon juice to your liquid (which should go to waste anyway). Vinegar has salt and plants don't grow well with salty water.

Answer 3

Actually, I discovered a way of eliminating fish odor that was apparently generated from an old can of salmon, which was in the process of bursting and leaking. The can was hidden on a lower shelf in my kitchen.

I originally believed there was an issue with something on the floor and kept on treating the floor until I produced results.

The exact process I employed, however, remains the subject of a future patent.

But, I will disclose that the apparent active agent is Singlet Oxygen (or, O(1D)). The latter could interact with oxygen in air further creating reactive oxygen species (see, for example, Equation (4) presented here). Apparently, O(3P) may be formed from severe collision quenching of O(1D) atom with oxygen and acts as the major oxidant, for example, in the work by Huan Yue and colleagues ‘Exploring the working mechanism of graphene patterning by magnetic-assisted UV ozonation’. Note, O(3P) is also known as highly reactive ground-state 3P oxygen and a form of atomic oxygen.

Of practical importance, singlet oxygen has a half-life of around 45 minutes and should be considered toxic, so treated areas should be evacuated prior to treatment. On contact with water, it forms hydrogen peroxide.

Note, unlike other de-odorizing agents that disguise smells, this path actually results in a chemical breakdown with no toxic or carcinogenic residual products.

Also, an associated 2008 patent: "Use of photosensitizer for cleaning air, water or contaminated surfaces and in filters, where the photosensitizer is covalently linked and/or linked over physical interaction to surface and activated by visible light to form singlet oxygen" discussed here.