Comparison of Swarovski and Zeiss Compact Binoculars for Birdwatching

Whether you enjoy the great outdoors or just want a closer look at the visitors to your bird-table, a good comfortable pair of binoculars makes for a more pleasurable experience.

Photo 1: Great Tit Landing on Nut feeder

Mary is the more avid birder (and much better at identifying our feathered friends) whereas I have a greater interest in avian behaviour. For years we managed with some cheap pocket-sized bins and this lumbering pair of Minolta Zoom binoculars weighing in at just over a kilogram...

Photo 2: Minolta Zoom Binoculars

The Minolta binoculars had a 7x to 21x zoom which was useful for general viewing although not so much for birdwatching because the image was not very bright despite the 50 mm objective lens. And you needed some support to stabilize the image on the higher magnifications. I've no idea what happened to the pocket bins but we still use the Minoltas occasionally for bird-table watches.

Back in 2015, while on holiday in Guernsey, we splashed out on a 'proper' set of bins for Mary. It may have been a joint birthday/Xmas present. Mary wanted a lightweight pair that offered a clear and bright image. After trying out a few different types, we plumped for the Swarovski CL Pocket 10x25 Binoculars (Photo 3, on the left) costing £479.95. That is quite a lot of money but they do ooze quality. These same bins are currently on sale for £700 (new) and even second-hand ones have kept their value (£450).

Photo 3: Binoculars under review

These Swarovski binoculars are robust, beautifully engineered, lightweight (350 g) and easy to use. The image is remarkably bright and sharp and they still feel as good as new after nearly 7 years. 

About 9 months ago, I decided to treat myself to a better lightweight pair of binoculars (compared with the Minoltas). My budget didn't stretch to the £700 of the Swarovski CL Pockets but I still wanted something half-decent. After doing the usual internet search/review, I opted for the Zeiss 522503 Terra ED Pocket 10x25 Binoculars (Photo 3, on the right) costing £319.

The Zeiss bins come in at less than half the price of the Swarovski's so some corners had to be cut. The build is solid enough and the engineering is decent though not in the same league as the Pocket CL. The focus wheel is large and easy to use but not as smooth running as the Swarovski's. Thankfully, Zeiss has not cut too many corners with the optics and the image is sharp and bright; not quite as sharp and bright as the Swarovski's but not too far off. On the plus side, the Zeiss offering comes in 10 % lighter (310 g vs 350 g) and you get a semi-hard case rather than the soft case with the Swarovski.

Using a mobile adapter for binoculars, telescopes, and microscopes (Photo 4), I have tried to compare the viewing experience of the Swarovski and Zeiss binoculars...

Photo 4: Mobile Phone Adapter

... by retaking the garden photograph from my View from the Rear Window series.

Photo 5: Rear Garden Photo (6th March 2023)

I was attempting to focus on the painted (by Mary) blue board at the bottom of the garden which is about 30 metres (100 feet) away. Note that Photo 5 was taken with a Lumix FZ38 camera whereas Photo 6 and Photo 7 were taken using the adaptor (Photo 4) and a Moto G(7) Play mobile phone. Both photos were taken within 45 minutes of each other on a sunny afternoon (24th March 2023) between 2.30pm and 3.15pm.

Photo 5: Zeiss Binoculars

Photo 6: Swarovski Binoculars

Hopefully, the differences will show up on the blog post but I would summarise as follows;

• Swarovski image is brighter than the Zeiss
• Image clarity is similar for both
• Depth of field is greater with Swarovski (compare image definition of the foreground cherry blossom approximately 10 metres away). 

The above test should not be considered definitive because it is certainly not trivial trying to achieve the same photographic conditions for both sets of binoculars. For example, the adaptor is a better fit for the Zeiss eyepieces and light conditions change between photo shots. Here are a couple of photos taken indoors to try and negate the effect of the lighting conditions.

Photo 7: Zeiss binoculars

Photo 8: Swarovski binoculars

As noted earlier, the mobile phone adapter fits the Zeiss binoculars better and you get a more defined circular image. The Swarovski image is a little brighter with slightly better clarity but the difference is not great (law of diminishing returns). If you can afford it and you want the best experience then you should go for the Swarovski bins. If you are happy to go with 'excellent' rather than 'perfect' then the Zeiss binoculars will give you many happy hours of birdwatching.

Britain's Best Wild Daffodil Display - The Golden Triangle

 

Photo 1: Panoramic shot of wild daffodils (Betty Daw's Wood)

Most people associate wild daffodils with Wordsworth and the Lake District:

I wandered lonely as a cloud (Daffodils)

BY WILLIAM WORDSWORTH

I wandered lonely as a cloud

That floats on high o'er vales and hills,

When all at once I saw a crowd,

A host, of golden daffodils;

Beside the lake, beneath the trees,

Fluttering and dancing in the breeze.

Continuous as the stars that shine

And twinkle on the milky way,

They stretched in never-ending line

Along the margin of a bay:

Ten thousand saw I at a glance,

Tossing their heads in sprightly dance.

The waves beside them danced; but they

Out-did the sparkling waves in glee:

A poet could not but be gay,

In such a jocund company:

I gazed—and gazed—but little thought

What wealth the show to me had brought:

For oft, when on my couch I lie

In vacant or in pensive mood,

They flash upon that inward eye

Which is the bliss of solitude;

And then my heart with pleasure fills,

And dances with the daffodils.

(courtesy of the Poetry Foundation)

However, if you want to see the very best display of wild daffodils, visit Gloucestershire during March for

the Kempley and Dymock daffodil weekends.

Photo 2: Wild Daffodils (Betty Daw's Wood)

The wild daffodil (narcissus pseudonarcissus) is fairly easy to spot, being smaller (less than 30 cm) than its commercial brethren with a deep yellow trumpet and pale outer petals. There are plenty of places around Kempley and Dymock to see the daffodils in all their golden glory with teas and cake to enjoy on the two special daffodil weekends. After tea and cake at Dymock, we drove to the small car park at Betty Daw's Wood - there seems to be some confusion on how to spell Betty's name!

It is only a very short walk from the car park before you are surrounded by a host of golden daffodils:

Photo 3: Betty Daw's Wood (25/3/23)

Photo 4: Betty Daw's Wood (25/3/23)

Photo 5: Betty Daw's Wood (25/3/23)

Wood anemones, violets and primroses were also on display:

Photo 6: Wood anemone in Betty Daw's Wood (25/3/23)

Photo 7: Wood anemone and wild daffodil (Betty Daw's Wood)

Photo 8: Wood anemone (with pale blue tinge) and wild daffodil (Betty Daw's Wood)

Photo 9: Primroses in Betty Daw's Wood (25/3/23)

Photo 10: Violets and Wood Anemone (Betty Daw's Wood)

Walking through Betty Daw's Wood brings you to a kissing gate into a field, then to a bridge over a small stream, through another wood (can be muddy) until you hit the road. Here you will find Gwen and Vera's Fields:

Photo 11: Noticeboard for Gwen and Vera's Fields

Last year, the daffodils were a little sparse but this year the display was back to its best:

Photo 12: Gwen & Vera's Fields (25/3/23)

On our return journey back to the car, we came across three Roe Deer crashing through Betty Daw's Wood. Mary managed to snap one of them (look for the two white rumps) in Photo 13:

Photo 13: Roe Deer in Betty Daw's Wood (25/3/23)

First Cutting of the Greensward in 2023

Many years ago we decided to dispense with our lawn (possibly better described as a patch of weedy clumps) and go with raised flower beds instead. Whilst grass cuttings are a very useful green feedstock for my hot composters, I don't think we have ever regretted getting rid of the lawn. Nevertheless, we are happy to encourage our neighbour to keep and maintain their lawn so they can pass the cuttings on to us. Maximum benefit with minimum effort.

With the increased difficulties of maintaining a hot composter over the winter months, I kept looking (with green envy?!) across at our neighbour's lawn thinking surely it's time to cut that! 

So, on returning from a visit to see the wild daffodils around Dymock on the 25th March (yesterday), it brought me great joy to come across the first cutting of the greensward for 2023.

Photo 1: Greensward first cut (2023)

Looking back, this turns out to be about the normal time for our neighbour to start cutting the lawn. In previous years the first lawn cut has been:

2020: 19th March

2021: 15th March

2022: 28th February

2023: 25th March 

At the moment, 2022 seems to be the outlier.

On a final note, I must say our neighbour's lawn is looking much better!

Photo 2: After the first cut (2023)

A Conversation with Bard - Urea versus Manure as a Fertilizer

Photo 1: HOTBIN Lid Thermometer & Vent (23/3/23)

In an earlier post on winterizing your hot compost bin, I discussed using supplements, such as urea and animal manure, to boost nitrogen levels in the hot compost bin when 'green' waste was in short supply during the winter months. I also mentioned that urea, as it is currently manufactured, comes with baggage such as its carbon footprint. While evaluating Google's new AI Chatbot (Bard), I entered into a discussion about the relative merits of urea and animal manure in terms of their carbon intensity. 

I asked Bard (Google's AI Chatbot) the following question:

What is the carbon footprint of urea manufacture? And its answer was ...

The carbon footprint of urea manufacture is significant. The process requires the use of fossil fuels, which release carbon dioxide into the atmosphere when they are burned. In addition, the process produces other pollutants, such as nitrogen oxides and sulfur dioxide, which can also contribute to climate change.

The carbon footprint of urea manufacture can be reduced by using renewable energy sources, such as solar and wind power, and by improving the efficiency of the process. However, even with these improvements, the carbon footprint of urea manufacture will still be significant.

The carbon footprint of urea manufacture is an important factor to consider when making decisions about fertilizer use. Farmers can reduce the environmental impact of their operations by using less fertilizer and by choosing fertilizers with a lower carbon footprint.

The follow-up question was:

Is the carbon footprint of urea worse than animal manure? And its answer was ...

The carbon footprint of urea is worse than that of animal manure. The production of urea requires the use of fossil fuels, which release carbon dioxide into the atmosphere when they are burned. In addition, the process produces other pollutants, such as nitrogen oxides and sulfur dioxide, which can also contribute to climate change.

Animal manure, on the other hand, is a natural fertilizer that does not require the use of fossil fuels. The carbon footprint of animal manure is also reduced by the fact that it is recycled back into the soil, where it helps to sequester carbon dioxide.

Therefore, the carbon footprint of urea is worse than that of animal manure. Farmers can reduce the environmental impact of their operations by using less fertilizer and by choosing fertilizers with a lower carbon footprint, such as animal manure.

However, it is important to note that the carbon footprint of animal manure varies depending on the type of animal, the way the manure is managed, and the climate. For example, the carbon footprint of cattle manure is higher than that of pig manure, because cattle produce more methane, a greenhouse gas. The carbon footprint of manure is also higher if it is stored in lagoons, which can leak methane into the atmosphere. Finally, the carbon footprint of manure is lower in warmer climates, because bacteria in the soil break down manure more quickly and release carbon dioxide into the soil.

Overall, the carbon footprint of urea is worse than that of animal manure, but the carbon footprint of animal manure can be reduced by using best management practices.

Then came the follow-up follow-up question:

Do you have any quantitative data? And its answer was ...

Yes, I do. According to the Food and Agriculture Organization of the United Nations, the carbon footprint of urea production is 1.2 kg CO2 per kg of urea, while the carbon footprint of animal manure is 0.6 kg CO2 per kg of manure. This means that the production of urea releases 2 times more carbon dioxide into the atmosphere than the production of animal manure.

It is important to note that these numbers are estimates, and the actual carbon footprint of urea and animal manure may vary depending on the specific conditions of production.

We are warned that Bard is not always correct but these data look about right. There is also a reference you can follow up. One of the good things about these AI-driven Chatbots, is the way it remembers your previous question; indeed, it is like you are in a conversation. My (follow-up)³ question was:

But isn't the nitrogen content of urea much higher than manure? And its answer was ...

Yes, the nitrogen content of urea is much higher than that of manure. Urea is a synthetic fertilizer that contains 46% nitrogen, while manure is a natural fertilizer that contains 2-3% nitrogen. This means that urea is much more concentrated than manure, and it can provide plants with a much higher level of nitrogen.

However, it is important to note that nitrogen is not the only nutrient that plants need. They also need phosphorus, potassium, and other nutrients. Manure contains a wider range of nutrients than urea, and it can also provide plants with beneficial microorganisms.

Therefore, both urea and manure can be effective fertilizers. The best fertilizer for a particular plant will depend on the specific needs of the plant and the soil.

I know the nitrogen content of urea is 46% and the reported content for manure is about what I would expect. Intuitively, one would think, urea is the preferred option as a nitrogen fertilizer because it has about 20 times the nitrogen but is only twice as carbon intensive as manure. Bard reminds us that nitrogen is only one of the nutrients required by plants and manure comes with other advantages. However, intuitively you would think that obtaining the other nutrients, such as potassium and phosphorus, might have a similar carbon intensity to urea manufacture so that a balanced artificial fertilizer might still be less carbon intensive than manure.

On to the next question:

Does that mean urea has a lower carbon footprint than manure when used as a nitrogen fertilizer?

No, it does not mean that urea has a lower carbon footprint than manure when used as a nitrogen fertilizer. When urea is used as a fertilizer, it releases nitrogen into the atmosphere as ammonia. Ammonia is a greenhouse gas that contributes to climate change.

Manure, on the other hand, does not release ammonia into the atmosphere. Instead, it releases nitrogen into the soil as organic matter. Organic matter helps to sequester carbon dioxide in the soil, which helps to reduce the amount of greenhouse gases in the atmosphere.

Therefore, the carbon footprint of urea is higher than the carbon footprint of manure when used as a nitrogen fertilizer.

Here Bard seems to be winging it. Manure most definitely does give off ammonia with upto 90% lost by the time it is applied as fertilizer. Urea, on the other hand, only loses about 16% of its nitrogen content as ammonia when applied as a fertilizer. Manure adds organic matter (humus) to soil which is definitely beneficial to soil health; however, some studies suggest that the soil does not hang onto the carbon long-term so may not be a viable carbon sink for the excess carbon dioxide in our atmosphere.

When questioned on this error of fact,  Bard was contrite and admitted to its error ...

I'm sorry but animal manure most definitely releases ammonia into the atmosphere.

Yes, I apologize for the error in my previous response. You are correct that animal manure releases ammonia into the atmosphere. Ammonia is a byproduct of the breakdown of nitrogenous wastes in animal manure. When manure is stored in a liquid state, ammonia can escape into the atmosphere as a gas. Ammonia can also be released from manure when it is applied to soil.

The amount of ammonia released from manure depends on a number of factors, including the type of animal, the amount of manure produced, the way the manure is stored, and the weather conditions. For example, pigs produce more ammonia than cattle, and manure stored in lagoons releases more ammonia than manure stored in solid form.

Ammonia is a greenhouse gas that contributes to climate change. When ammonia reacts with other chemicals in the atmosphere, it forms particulate matter, which can cause respiratory problems. Ammonia can also damage crops and other plants.

There are a number of ways to reduce the amount of ammonia released from manure. These include:

* Using best management practices when storing and applying manure

* Using anaerobic digestion to convert manure into a gas that does not contain ammonia

* Using nitrification inhibitors to slow the breakdown of nitrogenous wastes in manure

* Using technologies to capture ammonia emissions from manure

By taking these steps, farmers can help to reduce the environmental impact of animal manure.

I then posed the following question:

Based on this new information, is animal manure still better than urea as a nitrogen fertilizer?

The environmental impact of animal manure and urea as nitrogen fertilizers is a complex issue with no easy answers. Both have their own advantages and disadvantages.

Animal manure is a natural fertilizer that does not require the use of fossil fuels. However, it can release ammonia into the atmosphere, which is a greenhouse gas. Urea is a synthetic fertilizer that requires the use of fossil fuels. However, it does not release ammonia into the atmosphere.

The best fertilizer for a particular plant will depend on the specific needs of the plant and the soil. If you are concerned about the environmental impact of your fertilizer, you should talk to a local agricultural extension agent or a certified organic farmer.

A somewhat anodyne response with Bard sitting uncomfortably on the fence! As with many questions like this, it is almost certainly more complex than you think. Personally, I would rather use natural fertilizers though that would be garden compost (with added biochar) rather than animal manure. Urea is demonised because it is made in an industrial process that uses fossil fuels. Technically, its manufacture could be very green, and much greener than using animal manures, but it might still be demonised for being part of the industrial complex. On the other hand, those of us who adopt a more pragmatic approach to life might still want to use urea in a minimal and efficient way while, at the same time, encouraging a more environmentally sustainable means of production.

Some Benefits of Home Composting according to Google's AI Chatbot (Bard)

Bard is Google's AI Chatbot meant to rival ChatGPT and its clones. It is currently undergoing beta testing: you have to sign up to go on the waiting list but this only delays trying it out by a couple of days. 

I asked Bard to write a blog on the benefits of Home Composting. Here are a few of its responses:

Home Composting: The Benefits (First Attempt)

Composting is a great way to reduce your environmental impact and improve the health of your soil. It's also a relatively easy and inexpensive way to get started.

Here are some of the benefits of home composting:

• Reduces waste.
• Composting diverts organic waste from landfills, where it can produce methane, a greenhouse gas.
• Improves soil health.
• Compost adds nutrients and organic matter to soil, which helps to improve plant growth and reduce erosion.
• Saves money.
• Composting can reduce your need for fertilizer and pesticides, which can save you money in the long run.
• Is good for the environment.
• Composting helps to reduce greenhouse gas emissions and improve air quality.
• Is easy to do.
• Composting can be done in a backyard bin or even indoors in a worm bin.
• Is fun.
• Composting can be a great way to get kids involved in gardening and learn about the environment.

If you're interested in starting home composting, there are a few things you'll need to get started:

• A compost bin or worm bin.
• Organic materials to compost, such as food scraps, yard waste, and leaves.
• A little bit of time and effort.

Once you have your bin and materials, you're ready to start composting! Here are a few tips:

• Be sure to add a variety of materials to your compost bin. This will help to create a balanced compost that will be good for your soil.
• Turn your compost regularly. This helps to aerate the compost and speed up the decomposition process.
• Keep your compost moist but not soggy.
• Be patient! Composting takes time, but it's worth it in the end.

Composting is a great way to reduce your environmental impact and improve the health of your soil. It's also a relatively easy and inexpensive way to get started. If you're looking for a way to make a difference in the environment, consider starting home composting today!

Bard's responses have been described as 'boring' and 'anodyne'. There is a 'try again' button which seems to elicit a longer and more detailed response each time the button is pressed. For example, to the same question, Bard's second attempt was as follows:

Home Composting: The Benefits (Second Attempt)

Home composting is a great way to reduce your environmental impact and improve your gardening skills. When you compost, you turn organic waste into nutrient-rich soil that you can use to grow your own food. Composting is also a great way to reduce the amount of waste that goes to landfills. There are many different ways to compost at home. You can use a traditional compost bin, a worm bin, or even a bokashi system. No matter which method you choose, the basics of composting are the same. First, you need to find a location for your compost bin. The ideal spot is in a sunny location that is well-drained. You should also make sure that the spot is near a water source, as you will need to water your compost regularly. Once you have found a spot for your compost bin, you need to gather some materials. You will need some organic material, such as food scraps, yard waste, and coffee grounds. You will also need some brown materials, such as leaves, grass clippings, and newspaper. The next step is to start layering your compost. Start with a layer of brown materials, followed by a layer of green materials. You can then add another layer of brown materials, and so on. As you add materials to your compost bin, you should mix them together well. This will help to aerate the compost and speed up the decomposition process. You should also add some water to your compost bin. The compost should be moist, but not soggy. Once you have added all of your materials to your compost bin, you should cover it with a lid or tarp. This will help to keep the heat in and the moisture in. Now, all you have to do is wait! Composting takes time, but eventually, your organic waste will turn into nutrient-rich soil that you can use in your garden. Here are some additional tips for home composting:

• Start with a small compost bin. You can always add more space later if you need it.
• If you live in a hot climate, you may need to add more water to your compost bin.
• If you live in a cold climate, you may need to add more brown materials to your compost bin.
• Don't forget to turn your compost regularly! This will help to aerate the compost and speed up the decomposition process.
• Be patient! Composting takes time, but eventually, your organic waste will turn into nutrient-rich soil that you can use in your garden.

You are warned by Google that Bard's answers are not always accurate and this is illustrated in the second attempt where 'grass clippings' are described as 'brown' waste. Overall, though, I would say not a bad attempt.

My next prompt was to ask 'what are the advantages of hot composting?' and the response was not half bad:

Hot composting is a type of composting that uses heat to break down organic materials quickly. This method is often used to compost food scraps, yard waste, and other organic materials that would otherwise go to a landfill. There are several benefits to hot composting:

• It is a fast method of composting. Hot compost can be ready to use in as little as two weeks, while cold composting can take several months.
• It is a more effective method of composting. Hot compost kills pathogens and weed seeds, while cold composting does not.
• It is a more efficient method of composting. Hot compost uses less space than cold composting, and it produces more compost in a shorter period of time.
  

If you are looking for a quick, effective, and efficient way to compost, hot composting is a great option. Here are some tips for hot composting:

• Use a hot compost bin. A hot compost bin will help to keep the heat in and the moisture in, which is essential for hot composting.
• Add a variety of materials to your hot compost bin. This will help to create a balanced compost that is rich in nutrients.
• Turn your hot compost bin regularly. This will help to aerate the compost and speed up the decomposition process.
• Water your hot compost bin regularly. The compost should be moist, but not soggy.
• Monitor the temperature of your hot compost bin. The temperature should be between 120 and 160 degrees Fahrenheit.

With a little effort, you can easily hot compost your own organic materials and create a nutrient-rich soil that you can use in your garden.

Overall, I was quite impressed though there is still a long way to go. Is it better or worse than ChatGPT? I don't know but suspect each Chatbot will find its own niche where one outperforms the other.

An Ode to the House Sparrow written by ChatGPT

 ChatGPT is a chatbox powered by Artificial Intelligence (AI). I downloaded this version (Photo 1) of ChatGPT from Google Play:

Photo 1: ChatGPT version used

Then asked the app to write a poem about house sparrows ...

Photo 2: Part of our House Sparrow Colony

... and it produced this in about 30 seconds:

The house sparrow, small but bold,

With feathers brown, and wings to hold,

A heart so fierce, a joy to behold,

In cities and towns, it has grown so old.

It flits and hops, through streets and lanes,

A master of survival, with no refrains,

With food and shelter, it has made some gains,

A bird so common, that forever remains.

It builds its nest, with sticks and straw,

In gutters and eaves, it finds a flaw,

It lays its eggs, with nature's awe,

A cycle of life, without any flaw.

So let's cherish the house sparrow, a bird so dear,

A symbol of our earth, with no fear,

In its eyes, we see our salvation near,

A world that's pure, full of love and cheer.

My effort below took much longer ...

Our house sparrow colony

Lives in an old ivy hedge,

Making such a cacophony,

It sets your teeth on edge.

They visit the bird feeder

With regular monotony.

Playing follow my leader,

That's our house sparrow colony.

The constant trills

From our house sparrow colony.

So devoid of frills

Without even an apology.

Yet, when Autumn comes round,

And the birds fly away,

To the countryside bound,

And we hoped they would stay.

After their rural retreat,

We'll welcome the throng

Back here to eat

So we can enjoy their song.

Hot Composting #5 (Winterizing your HOTBIN)

In case it wasn't obvious, I am rather keen on composting. I have written some general composting blogs (here and here) as well as some niche ones (here and here). Furthermore, in previous blogs (here, here, here, here, and here), I have extolled the virtues of hot composting (as opposed to the more widely-practised cold composting technique) and described some of the basic principles, ideas, and methods behind hot composting. There will be more articles on this topic, both niche and mainstream.

It is easier to compost during Spring, Summer, and Autumn when the weather is mild/warm and there is a plentiful supply of green waste. With the typical cold composting process, everything grinds to a halt during the Winter - you might add stuff to the compost heap but its origins will still be recognisable when Springtime comes around!

Photo 1: HOTBIN composter contents (visible)

Photo 2: HOTBIN composter contents (infrared)

Hot composting opens up the possibility of composting all year round. To counteract the colder, even freezing, outdoor temperatures it is essential your hot composter is well insulated and that you can supply a regular source of green (nitrogen-rich) organic waste. The HOTBIN is ideal due to its seamless construction, thick (5 cm) insulating walls, and tight-fitting lid; moreover, the design of the HOTBIN obviates the need to 'turn the heap' and introduce lots of cold winter air.

An infrared photograph of my HOTBIN is shown in Photo 3. The photograph was taken at 10.45 am on the 24th of February 2021 using the FLIR One Pro attached to Moto G(7) Play; it was a sunny day with an outside temperature of 11 ℃ and the HOTBIN was about 80% full (Photo 4). The upper part of the HOTBIN is hotter, because that is where the hottest compost is (Photo 4), and there appears to be some heat leakage between the lid and bin. You can also see the 'hot' steam exiting from the lid vent.

Photo 3: Infrared Photograph of HOTBIN (24/2/21 @ 10.45 am)

Photo 4: Infrared Photograph of HOTBIN contents (24/2/21 @ 10.45 am)

As noted above, a regular supply of green (nitrogenous) waste is necessary to keep the micro-organisms (e.g. bacteria) in your compost bin multiplying ad infinitum and generating the internal heat that will keep your 'heap' cosily warm. Of course, you still need to add 'browns' to the heap but there is generally no shortage of these during winter. Unless you are still mowing the lawn or pruning evergreen bushes/trees, it is the 'greens' that are likely to be in short supply. Kitchen waste is a good source of 'greens'; however, you may need to be creative in finding other sources if the contents of your kitchen caddy are insufficient or you cannot convince your neighbour to mow his lawn in the middle of winter.

• Animal 'manures' - e.g. chicken, cow, horse - are a great source of nitrogen if you have access to this resource.
• Pelleted chicken manure is a more convenient form of nitrogen (and other nutrients) that can be added as a solid or liquid.
• Urine is free and a good source of nitrogen and other plant nutrients (Footnote #1); it is also rather wet and so should be used sparingly - a wet compost heap does not compost well! Adding some adsorbent material, such as shredded card/paper or crumbled coir block (Photo 6), at the same time should minimise any overwetting issues.
• Urea is a cheap and readily available nitrogen source that can be added sparingly as a solid (if compost is damp) or liquid solution (if compost is dry). You may see it sold as 46-0-0 fertilizer. Unfortunately, fossil fuels are used to produce the ammonia needed for the manufacture of urea, with an estimated carbon footprint of between 0.4 and 1.1 tonne CO2 per tonne of urea produced. If this estimate is correct then scattering 50 g urea prills into your HOTBIN has the same carbon intensity as half a banana (Footnote #2)
• I have not tried general fertilizers such as Blood, Fish & Bone or Growmore. My understanding is that the nitrogen availability is relatively 'fast' even in these slow-release fertilizers. Blood Meal is the high-nitrogen product in Blood, Fish & Bone. I will probably give one of these a try in the future to see whether they work as compost activity boosters.
• Compost Accelerators - predominantly an expensive source of nitrogen. They may also include some beneficial microbes. Use as a last resort.
• Comfrey or Nettle Tea - both contain a good bit of nitrogen though nettle tea is superior in this respect. I always seem to have some left over at the end of the growing season. Add small amounts (100 or 200 ml) neat without dilution.
• Ivy - a good evergreen winter standby that composts well when shredded. We share an ivy hedge (see if you can spot it in Photo 3) with three neighbours and it is a favourite roosting & nesting site for our local house sparrow population. Consequently, I use this resource very sparingly in my compost bins.

Photo 5: Resident House Sparrows enjoying the Garden Birdfeeder

Having taken care of the compost bin's dietary needs, it is now time to consider some physical methods for maintaining or upping the temperature of the active composting part of the bin to >50 ℃. I do this in two ways:

• Add hot water bottles: The original Kick Start Bottle that came with my HOTBIN is no more - I cannot remember whether it developed a leak or the cap broke. In any case, I re-purposed a couple of 2.5 litre bottles that once held organic patio cleaner. I add about 1.8 litres of boiling water (a kettle-full) to each bottle and bury it in the compost pile (Photo 6). I save a bit of time and energy by filling the kettle from the hot water tap. It takes 0.12 kWh of electricity, with a carbon footprint of about 40 g CO2e, to raise 3.6 litres of water from the hot tap (45 ℃) to boiling point. I, typically, use two bottles to provide a bigger kick start to the composting process providing about 450 kJ of energy to the compost pile.

Photo 6: Winter HOTBIN with hot water bottles

Table 1 summarises the 'hot water bottle' effect on compost temperatures over a 24 hour period. Following a frosty night on March 9th (when the outside temperature dropped to -2 ℃), the temperature in the uppermost part of the compost pile (10 cm) had dropped to 37 ℃. Two hot water bottles (HWBs), along with 8 litres of organic waste (including 2 litres of green kitchen waste), were added at 10 o'clock in the morning. By 4.30 pm, compost temperatures had increased at all three depths with the top section of the pile now at 50 ℃. The two HWBs were replaced with fresh ones because we were expecting more subzero temperatures that night. Despite the overnight temperatures dropping to -3 ℃, the topmost section of the pile rose to 55 ℃ by 10 o'clock the following morning. Note, the addition of green waste or some other form of nitrogen is important (see above). 

Table 1: Increase in Compost Temperatures When Using Hot Water Bottles

DATE/TIME	Minimum Overnight Temperature	Compost Temperature @ 50 cm depth	Compost Temperature @ 30 cm depth	Compost Temperature @ 10 cm depth
10/3/23 @ 10:00h	-2 ℃	18 ℃	24 ℃	37 ℃
10/3/23 @ 16:30h	-	24 ℃	33 ℃	50 ℃
11/3/23 @ 10:30h	-3 ℃	19 ℃	33 ℃	55 ℃

At 40 ℃ and above, bacteria in the compost become superactive and will rapidly multiply provided they have access to a usuable nitrogen source. Heat is a by-product of this growth. The HWBs are creating warm spots in the otherwise 'cold' heap where the bacteria multiply and generate more heat which spreads to other parts of the heap enabling even more bacterial growth generating even more heat ... 

The HWB technique can also be used to get a new compost heap off to a rapid start.

• Cover the top of the Heap with a Mat: We saw in Photo 3 that most of the heat leakage is around the lid of the HOTBIN. Heat loss through the vent in the lid is necessary for the HOTBIN hot composting process to work. Heat loss around the edges of the lid should, however, be minimised. First of all, check the contact surfaces of the lid and base are free of detritus as this will stop the lid closing fully. Then consider adding a breathable mat to insulate the top of the compost pile and reduce heat loss.

Photo 7: Breathable Insulating Mat

There are a number of reasons why you should consider using a top mat in the HOTBIN which I discuss here. In winter, its most important property is to insulate the top of the pile to reduce heat losses by convection, especially when the HOTBIN is only partially full. There is little point heating the space above the pile where there isn't any composting to be done. It is important the mat is breathable and not tight-fitting so that the chimney effect, on which the HOTBIN relies, continues to work. For this reason I use a piece of thick capillary matting. 

Footnote #1: Urine is a dilute solution of urea plus lots of other chemicals and micro-organisms. It can be used as a fertilizer (see here, here, and here) as well as a number of other uses. In terms of its key fertilizer properties, as-received urine has an NPK value of 0.7-0.15-0.22. It is the relatively high nitrogen content (about 1 %) that makes it a useful compost accelerator when used sparingly - the 95% water content is a bit of a disadvantage so include dry/adsorbent material when using!

Footnote #2: I must admit I was a little sceptical of this estimated value (0.4 - 1.1 tonne CO2 per tonne of urea) for the carbon intensity of urea production - it seemed on the low side so I had to wonder whether they had considered all the possible inputs. Quantifying the carbon footprint of a complex chemical process is not a trivial task so I decided to try another information source - How Bad Are Bananas? by Mike Berners-Lee. This reference estimated a carbon intensity of between 1 and 4 tonnes CO2e for each tonne of nitrogen fertilizer (ammonium nitrate) produced depending on the efficiency of the process. So it seems a value of 1 tonne CO2 per tonne of urea is not unreasonable for the carbon footprint. Hopefully, this carbon intensity will reduce in the future through more efficient processes leading ultimately to green urea production.