Posts Tagged ‘recycling’

Sustainable Intensification

December 27, 2012

Sustainable Intensification, is there something more there than an emergency solution coined by the Royal Commisssion when nothing else was at hand: more production is needed (caused by increased consumption), further land resources are scarce, water is scarce, the environment cannot take further loads, on the contrary – that should be reduced. Increased production on the land we use seems a necessity.

So – there is substance. It is clear that we can improve the present agricultural production in different ways. Let us just focus on it.

A Swedish project “FramtidsOdling” will work on that focus.

“Framtidsodling” means literally Future Farming, or rather Future Crop Production. Ideas of an English name will be welcome. Future Farming seems a bit over-used.

Recycling is another general topic which has engaged me a lot in 2012. A project within the Royal Academy of Agriculture and Forestry will end up in a seminar in Febr 2013. We need recycling, but not at any price. It should have a positive net effect at least on long term basis. There are many aspects to consider and often an unambiguous solution is not evident. But at least might be possible to find a system for evaluation of different alternatives.


Sausage, biochar and recycling.

December 19, 2012

I fancied a sausage. There is fire in the fire-place, I can grill there. Place it in a metal folie container, then I can do other things. But the heat and fire was more intense than expected, and when I looked the whole sausage was on fire. Black as coal. But I could extinguish. And – underneath the coal layer  it was quite fine. But smaller.

It made me think about biochar. That is a kind of burning (ok – pyrolysis), preferably of biomass, some gases are collected and there is a rest, biochar. Applied on soil it is stable for a long time. The carbon dioxide captured by the biomass will then be permanently withdrawn and stored as carbon in the soil. It is a way to store carbon and reduce climate gases.

But I have a sceptical thought: You have let us say one kilo biochar. You could burn it in an energy production unit and in that way save one kilo fossil carbon otherwise needed. Or you could store it in the soil. Is the difference important? Some say so, also scientists and professors, but I am not totally convinced.

Biochar should make the soil more fertile. It has a large active surface (but not as large as clays, it absorbs water and improves soil structure (but what amounts are needed to make practical impact?). There is a nutrient content, but that factor is not much mentioned. The P and K present in the biomass should end up in biochar.

Wonder products make me sceptical, maybe too much.

Maybe sewage sludge could be used for biochar?  That should give a product combining carbon, P and K for agriculture.  The metals will also be there, I am afraid.

An important environmental problem is organic substances (hormones, medicins, the chemical palette used in our society) which pass the sewage work and end up in waters. Promising attempts have been made to absorb at least some of them by means of active carbon. That sounds expensive. Is biochar active?

Then you could imagine a nice combination: Biochar is added in the sewage treatment, it absorbs harmful organic substances and ends up in the sludge. The sludge is incinerated, the biochar gives extra energy, all organic substances are eliminated, the ash is extracted and a pure P fertilizer results. Especially advantageous would be if the biochar is produced by another sewage work where burning and extraction is not feasible. Biochar production could be more smallscale. You get a more transportable product and the P from both works are taken care of.

If someone will use this idea, kindly refer to this blog.

Recycling. Phosphorus should have priority.

November 24, 2012

The food we eat contains nitrogen and phosphorus, important elements for everything living. It ends up as toilet waste. After treatment in sewage works most of the phosphorus and some of the nitrogen end up in sewage sludge. This contains also some heavy metals, bacteria, hormones, medicins and various chemicals.  Sludge (biosolids) is a kind of fertilizer containing especially phosphorus but some nitrogen and above-mentioned impurities. To apply it on food-producing soils , is that right?

There are processes where the sludge is burnt, pure phosphorus compounds are extracted and a clean phosphorus fertilizer is produced. Then we miss the nitrogen. Is that right?

Systems can be developed where the toilet waste is collected, hygienized and used more directly as fertilizer. Then we take care of both phosphorus , nitrogen as well as potassium and other nutrients. Unfortunately hormones , drugs and chemicals are included.  Physically it is a thin sludge to transport and distribute. Is that right?

We need some guidelines to choose.

Phosphorus is special for two reasons:

1. It is a limited resource. We know about mineral deposits for 10-20 generations, but then ?

2. All we take out from mineral deposits ends up in our environment, in fields, gardens, waste dumps, waters.  It is active and causes eutrophication. And we never get rid of it. It might move, but is still active.

These are two, as I see it, overriding reasons to give phosphorus priority, to keep down extraction from mineral deposits by recycling as much as possible.

Nitrogen is different.

1. We have unlimited resources,  80% of the air is nitrogen. But we need energy to make it active, and all kinds of energy can be used. The present oil and gas can be replaced by hydro- or solar energy or even bioenergy.

2. An important process, denitrification, removes active nitrogen from the biosphere and gives it back to the air. There is no unavoidable  accumulation.

3. Active nitrogen (ammonia, nitrate, nitrogen oxides) are environmenal pollutants. Research has suggested that we already exceed the limits of the globe in this respect.

The main priority for nitrogen is to avoid losses of active nitrogen. To handle the farm nutrients as efficiently as possible. (Organic nitrogen in for instance sludge is in fact a disadvantage in this respect). Environmental analysis should guide the development

Conclusion: Extract pure phosphorus when possible. The loss of nitrogen is no great disadvantage (provided there is no nitrogen pollution from that process)

There are local needs for more smallscale processes.


January 7, 2011

These days I am working with a paper on recycling of sewage. There are problems, unwanted metals and organic agents of different kinds.

How important is recycling of waste from sewage works? On a closer look I was surprised. It is not as crucial as I had thought.

Sweden does not produce its own food demands. Yes, we could, but there is the market.

But we eat well. Export industrial products and buy food as well as export some. There is an exchange as it should be. And we produce waste for the sewage works.

The best technology can do is to take care of all nutrients going to the sewage work and use them in agriculture. Impossible, but let us look at this unattainable potential. If we recycle everything only 20% of the plant nutrient demand would be covered.

Phosphorus is special. The reserves are limited and it is an active element in the environment. So P recovery seems essential. But other elements should not complicate this development. Nitrogen is an energy issue and potassium reserves are not critical.

Organic matter? Well, it is important for the soil as such, but sludge is a small post in this context.

A primitive energy consideration: We have 1 kg sludge, dry matter. We can use it in energy production and get 10 MJ. For 10 MJ we can produce 0,25 kg N. W use that in a good agricultural production and get 10 kg organic matter, to use for food, feed or soil improvement.

Yes, there are considerations of energy quality. But there are also margins. And varying technologies to use.

On nitrogen recycling.

November 29, 2009

 To reduce input of reactive nitrogen to the biosphere improved use of the nitrogen in our waste flows could be important. What do we know?

 Sewage sludge: contains only a small fraction of the total sewage nitrogen flow.

Waste water irrigation. Discussed as a necessity/possibility in some parts of the world. But considering our discussion about impurities and risks with sewage sludge a largescale development does not seem likely.

Re-capture of the nitrogen in sewage works. Norsk Hydro had a practical process in one of the sewage works of Oslo. Driving off ammonia and capturing it in acid to ammonium nitrate solution. Worked commercially in limited scale. Another possibility which has been proposed is precipitation of magnesiumammonium phosphate (struvite). It captures phosphate and some nitrogen. In a new situation such processes can be further developed.

Separation of urine and faeces, use of urine as fertilizer. Takes care of most of the nitrogen. But there is a storage- and transport problem, especially for large cities. But definitely a possible part of a future system.

Composting. Compost has a good reputation but is a process wasting nitrogen.

For developing countries there are developments like Pee-Poo bag.

However, there is another principle, not unlike our present system: we transform the reactive waste nitrogen to unreactive gas and fetch it back in an ammonia factory. Then the nitrogen issue is transformed to an energy issue.


February 3, 2009



The conference in Cambridge in December about recycling development is really worth noting. Important circles in the international fertilizer sector take recycling seriously. Only this fact is interesting. Much development is going on in the world, and fast. An observation full of hope.

“We must change – or suffer lack”, as Johnny Johnston from Rothamsted said in the introductory lecture.


Maybe not so many new facts were presented in the conference, but many good summaries. Recycling is difficult. We want the good things, phosphorus, nitrogen and organic matter but not cadmium, medicins and bacteria. But to separate these completely is not possible. We have to develop and work with the best technology and processes and balance advantages and risks. The goal cannot be zero risk, that is not possible in the society.


Source separation of especially urine seems both efficient and safe. But it takes a long way of development.

And again I have to mention the PeePoo bag. A hygienic and directly recyclable single use toilet.

Country differences.

January 30, 2009

At the conference in December arranged by The International Fertiliser Society (see tag Recycling) phosphate was an issue. We have to economize with this limited resource. Some figures for UK (minus N Ireland) were mentioned, meaning that the agriculture (and river banks) looses about 0.8 kg P per hectare agricultural land (incl pastures) to surrounding seas. We in Sweden are struggling to reduce a loss of 0.4 even further.


In England the Cd content in sewage sludge now is reduced to 70-120 mg Cd/kg P (“not much different from mineral fertiliser”). The Swedish figures are about 40 and 10 respectively.

The regulations for sewage sludge in England say that the content 3 g Cd/kg soil shall not be exceeded and the additions of Cd are maximized to 150 g in a ten year period. The average Cd content in Swedish soils is about 0.5 g/kg and we do not want any increase at all. The goal is balance, but a problem is that about 0.5 g/hectare is deposited from the atmosphere.


For phosphorus it might be a question of stage. We started to adapt the nutrient management a couple of decades ago and are leading in Europe.

The base for the differences in cadmium is unclear. Different interpretation of scientific reports?

But this favourable situation for Swedish agriculture gives no advantages for the farmer, only costs. And more pressure.That is the problem with products influenced by commodity pricing in a global scale.



December 14, 2008

was the subject for the Annual Conference of the International Fertiliser Society (IFS). IFS is a professional society for plant nutrition in a wide sense, from industrial technology and logistics to agronomy and environment. Recycling is not a new question in this context, but the strength and importance given to recycling in this conference is remarkable.


In focus:


Phosphorus – a finite resource. Improved recycling is a necessity. “Peak oil”  is an accepted concept. It is also relevant to speak about “peak phosphorus”. We must change – or suffer lack.


Sulphur may also be a scarce resource. Maybe old deposits (gypsym) may need to be used.


Environment and resources in a world with growing demands.


What can be done? Some points to further develop:

Policies and regulations for waste products for recycling.

Hygienization and product development.

The PeePoo bag. A single use toilet, hygienic, ready for recycling to soil. Could be of great value for the world.

Matchmaking between industries and enterprises to diminish waste and increase efficiency.

Manure use, biogas, bioenergy in general.

Biomass and maybe phosphorus recycling from the seas?