Archive for September, 2007

Fun Science – How many megabytes in the human body?

Following on from my post about the incredible progress of computer storage density over the last twenty years, I remembered hearing a ‘popular science’ broadcaster here in Australia equating the gamete transfer during sexual reproduction to data transfer.

I like ‘weird science’ so I thought I’d go back and try and ‘reproduce’ his findings (pun entirely intended) – so – in this post I’m going to explain in ‘digital terms’ (eg megabytes, gigabytes):-

  1. The number of megabytes of ‘data’ exchanged during human reproduction.
  2. The amount of data which the human brain can store (hypothetical).
  3. The amount of data stored in all the cells in the human body.

This post involves some low-level discussion of sexual reproduction. So, if you’re prudish or get offended by this kind of thing, I apologise in advance and please turn away now 🙂

The amount of ‘storage’ in the human brain

We can do similar calculations with the human brain – although these are much less definite – we’re much less certain about how the brain works than we are about how sexual reproduction works.

The average brain has around 100 billion brain cells (neurons) – that’s 100,000,000,000 brain cells (although this is a ‘guesstimate’ based upon other factors).

Human Neuron - like a bit of data?Each neuron is functionally connected to around 1000 neurons (again, a guesstimate). If we assume that neurons have either an ‘on’ or ‘off’ state (digital logic – although, not unsuprisingly, we have reason to believe that brain storage uses analogue voltage ‘levels’ rather than digital logic for storage) we can then assume that each neuron can ‘read or write’ 1000 neurons – essentially 1000 bits or 0.122 kilobytes of data.

Assuming that this ‘data’ ripples through the brain in a steady-state manner, we can assume that the average amount of ‘storage capacity’ is hence 100,000,000,000 by 0.122 kilobytes, or 122 million (122,000,000) kilobytes. If we convert that figure to gigabytes, we arrive at the sum of 116.34 Gigabytes of data in digital terms.

Obviously there is a massive fudge factor here – the calculations make alot of very ‘broad’ assumptions – it’s really just a ‘fun’ measure of what our brain capacity would be if it was a digital system.

How many Megabytes in the Human Body

This one’s just too complex for me to consider this early in the morning – but lets have a go (drawing on my limited recollection of genetic biology here).

I’d guess to work it out you’d have to define each ‘base pair’ as a bit of information.

In human DNA there are two common base pairs which consist of the ‘nucleotides’ adenine, thymine, guanine or cytosine. Generally speaking only adenine and thymine pair with each other, as do guanine and cytosine – so the typical DNA base pair can be AT or CG – one of two states – a bit.

The DNA Double Helix, and 'digital' base pairs

The human genome is estimated to contain some 3 billion base pairs – so (again, simplifying) 3 billion bits = 0.35 gigabytes – so each cell in our body encodes roughly a third of a gigabytes of information – that’s a pretty high information density, especially considering that the double helix DNA in our cells is a minute proportion of the cell as a whole (and that the process of cell reproduction produces RNA strands which may be present in a cell as well).

Estimates for the number of cells in the human body range between 10 trillion and 100 trillion (see Sears CL. 2005. A dynamic partnership: Celebrating our gut flora. Anaerobe, Volume 11, Issue 5, October 2005, Pages 247-251).

The generally accepted figure is 100 trillion cells – so, given each cell contains 0.35 GB of data, the (very) approximate amount of data held in human cells is 35 trillion gigabytes, or 34,179,687,500 terabytes of data, or, expressed in megabytes 3.58400 × 1016 megabytes!!

If you add in the information encoded in RNA and the base pairs in the bacteria which live in our body (another 1000 trillion cells) then we’re talking about a hell of alot of data.

The human race would make a truly excellent data center if Google ever runs out of storage space or we get invaded by aliens with a need to store lots of information 😀

The number of Megabytes ‘exchanged’ during human reproduction

The human sperm can be one of three states - x, y or wasted.Each sperm cell in a human male is heterogametic, meaning it contains only one of two sex chromosomes (x or y) – incidentally, the female egg is homogametic – meaning that it only has an x chromosome.

This means the male ‘determines’ the sex of the child, which makes a mockery of Henry the 8th’s annulment of his marriage with Catherine of Aragon on account of the fact that she was ‘incapable of providing a male heir’.

Basically, sperm cells are like bits – they can (in most cases) be only one of two states – x or y, or in digital form, 0 or 1. So, it’s possible to express an ejaculate in megabytes (!?!) – Let’s try.

The average human ejaculate contains around 180 million sperm. So, that’s 180,000,000 bits. If we use google to convert 180 million bits to megabytes, we find that approximately 21.45 megabytes of ‘data’ is transferred during each act of human sexual reproduction in the form of gametes.

Whether this ‘information transfer’ results in anything constructive is up to individual circumstance, but it does raise a number of interesting questions (I’m putting my communications enginner / silly hat on again):-

  • Given that this is ‘bursty’ traffic, what is the peak data transmission rate (in megabits per second)?
  • How does this compare to optical fibre (assuming the subject doesn’t suffer from ‘dark fibre’ problems 😀 )?


Have you got any other ‘fun science’ questions you’d like answered? Any comments? You can leve your comments below.

23 comments September 27th, 2007

Curing the oil crisis:- Starch or Sugar based Ethanol versus Cellulosic Ethanol

Ethanol as a replacement for petroleum

Back in my undergrad degree, I did some research into the viability of using resources from Australia’s large sugar cane industry as a feedstock for ethanol production.

My research was completed about 10 years ago. I found that for Australia to fulfill its own oil demands with Sugar Cane based ethanol it would need to have the entire arable land mass of Australia under cane and that the cost of production would be around 60c per litre, or about US 2.26 per Gallon.

The Australian retail price of petrol back then was around the 60c mark. It was clearly an impractical and uneconomic proposition.

Replacing Oil with Ethanol?

I went on to spend some time with the Sugar Industry and I found along the way that really my calculations were entirely flawed.

Firstly, I’d assumed that the feedstock for my theoretical ethanol production would be something called Molasses. Molasses is relatively cheap and abundant by-product of sugar production and is often used to produce rum. It contains perhaps 5% of the available sugar produced from the processing of Sugar Cane – with the remainder generally converted into relatively high value crystal sugar (the type we use in our coffee).

Two things have changed since then – the world price of sugar has precipitously declined and the world price of oil has sky-rocketed – so the economics have changed. I thought I’d take this opportunity to cast a backwards glance and go over my figures once again.

Brazil can switch between ethanol and sugar production almost instantaneously!

Brazil (the largest producer of sugar cane in the world) has over the last 10 years or so built the capability to easily tailor their production to either crystal sugar or ethanol – basically if the oil price is high, Brazil starts producing ethanol.

Due to the enormous size of the Brazillian industry the resultant shortfall in crystal sugar tends to drive up the world sugar price – so much so that over the last 5 years or so we’ve started to see the world sugar price (WSP) follow the peaks and troughs of the oil price.

Already, without even realising it, Sugar has become an agro-industrial energy crop. The same thing has happened with corn as well – in recent years the price of maize has doubled in much the same way as the price of oil has.

This is a very different playing field to that I investigated 10 years ago – ethanol production from sugarcane is now starting to become an economic proposition of some merit.

A friend of mine in the south of India has secured the rights to build an ethanol factory in a state called Kerala, so I’ve been speaking to some experts here in Australia on his behalf about the new state-of-the-art in ethanol production.

Cellulosic Ethanol

Kerala has a rather large Coconut industry, and one of the interesting possibilities we are looking at is cellulosic ethanol, which has recently been featured in this great article from wired magazine.

This is still a technology in its infancy, but things are looking very promising. Cellulose is the stuff that makes plants stand up – it’s tough, it contains a great deal of Carbon and it’s not easy to break down.

For all our evolutionary complexity, we as humans haven’t yet developed the ability to utilise cellulose as an energy source in our diet, although that’s not the case for other organisms.

Ruminants like cows, goats and camels are capable of supporting vast populations of bacteria in their gut which digest the cellulose and produce by-products called (again, simplifying) short chain fatty acids which can then be digested by the animal as an energy source.

Termites go a step further – their guts apparently produce these enzymes in-situ without the need for a symbiotic colony of gut bacteria.

In recent years there has been a veritable explosion in the number of companies (and governments) investing in this particular technology.

What are the expected yields of alcohol per tonne of Cellulose?

It’s very hard to find definitive numbers here though that allow us to start looking at the potential economics of using cellulose from plants as a ethanol feedstock.

One article about the economics of cellulosic ethanol production states that the theoretical yield of ethanol per tonne of biomass is 114 gallons (431 litres), but in practice the real (achieved) yield is closer to 70 gallons (264 litres). Unfortunately that particular article doesn’t express ethanol production as percent dry biomass (aka dry matter) so it’s hard to compare it with other studies.

Another article I found goes into a bit more detail and compares potential cellulosic ethanol production between four feedstocks – corn stover (another name for corn stalks), alfalfa stems (lucerne), sugarcane bagasse (the dry fibre left over after sugar extraction, usually burnt as a waste material) and Oak Wood. This particular study expresses Alcohol production as litres of ethanol per tonne of dry matter – a much better measure.

Conversion efficiency (%)
Feedstock Hemicellulose
to xylose
to glucose
Alfalfa stem 96 88 228
Corn stover 92 90 298
Sugarcane bagasse 90 86 267
Oak wood 88 79 278

These figures tend to correlate well with those given in the first reference – that expected production of ethanol per tonne dry biomass is going to be somewhere in the order of 220-280 litres of ethanol. It also correlates fairly well with a ‘tool’ provided by the US Department of energy which allows you to calculate the theoretical yield of cellulosic ethanol based upon the composition of a biomass feedstock.

So.. down to some economics..

Let’s take a reference (underestimate) of dry matter % sugarcane biomass as ~14%. So, for every 1000kg of sugarcane, we’ll assume we’re left with 140kg of dry cellulosic materials after extraction of the sugar. Assuming 260 litres per tonne biomass, that means that we’re going to expect to produce around 36.4 litres of cellulosic ethanol per tonne of harvested sugarcane.

Now the important part – Sugarcane uses what’s called C4 photosynthesis – meaning it’s extremely effective at producing biomass from sunlight – biomass yields are very high and the plant is extremely fast growing. A typical yield of sugarcane per hectare in Australia would be ~ 70 to 150 tonnes cane per hectare per annum. We’ll take the midpoint – 100 tonnes.

This means that from cellulosic sources, we’d be expecting to produce around 3640 litres (961 gallons) per hectare of cane from a material that is otherwise considered a waste product.

What about if we used the sugar too?

Now lets look at the sugar content.

Fleay et al (2006) states that (one tonne of) “sugar yields 0.385 tonnes of anhydrous ethanol” and the specific gravity of ethanol is somewhere between 79% and 81% that of water, meaning we can expect the yield of anhydrous alcohol per tonne of sugar to be (1/.8*385)=481 litres.

In general the CCS of cane (amount of sugar in a tonne of cane expressed as percent biomass) is somewhere between 10 and 14% – and that doesn’t include the sugars available in molasses. Let’s assume that we just macerate the cane, extract the juice and ferment that (a much less energy intensive process than extracting the sugar) – we’ll make a relatively broad assumption that we’ll have around 140kg of sugars available per tonne of cane, which, at our theoretical yield of 100 tonnes per hectare equates to around 14,000 kg sugar per hectare available for fermentation and conversion to ethanol. At 481 litres per tonne of sugar, we’ll be left with around 6735 litres of ethanol per hectare.

So.. we’re left with the following figures.. from a ‘typical’ cane field with 14% fibre, 14% available sugar and 100 tonnes per hectare..

Yield of Cellulosic Anhydrous Ethanol per hectare – 3640 litres

Yield of Fermented Anhydrous Ethanol per hectare – 6735 litres

Total yield of Anhydrous Ethanol per hectare – 10,375 litres

Could Ethanol totally replace our petroleum usage?

Would this be enough to satisfy Australia’s Oil needs?

Let’s assume an annual cane yield of 40 million tonnes, or roughly 400,000 hectares under cultivation – this equates to around 4 150 000 000 litres, or 4.15 billion litres of ethanol per annum (assuming one crop cycle per year)

The energy density of ethanol is only around 70% of that of petroleum so this would equate to around 2 905 000 000 litres (2905 megalitres) of petroleum (although ethanol does have a higher octane rating, which means it burns more efficiently, so this is probably a slight underestimate). Current petroleum consumption in Australia is around 20,000 megalitres per annum, leaving a shortfall of over 17,000 megalitres per annum.

WOW! If Australia was to convert our entire sugar industry to the production of ethanol, we’d only be able to satisfy around 14% of our demand for automobile fuel (not including diesel consumption which is another 4000 megalitres). Keep in mind Australia has only 20 million people.

The scale is enormous – in QLD you can basically drive for 2000 uninterrupted kilometres and all you’ll see growing is sugarcane.

If we wanted to gross up our cane production to satisfy our demand for foreign oil (for automotive use only), we’d need to have around 2,857,000 hectares under sugar cane – the entire cropable landmass of Queensland (approx 20% of Australia’s land mass) is just below that figure. Forget about eating – we’d need to crop our whole state just to satisfy the thirst of the nation’s automobiles. That’s quite amazing and I feel the figures for a country with a much higher population density like the US would be even more compelling – these are interesting figures.

This reinforces a few things to me:-

  1. The massive scale of our oil consumption is easier to comprehend when it is expressed as biomass equivalent production (the amount of oil beneath the earth was phenomenal)..
  2. That burning that finite resource to fuel inefficient vehicles rather than using it for higher value industrial purposes for which no other economic feedstock exists (plastics, medicines etc) is perhaps not the best long term use of an amazing natural resource.
  3. That folks are going to look back at this period of history and wish we had done things a bit differently.

What are your thoughts? Where do you think the future lies? I’d be keen to hear your ideas / opinions.


THE AUTHOR: Matthew holds degrees in Agricultural Science and Computer Engineering. Matt has extensive experience in the Sugar Industry worldwide and has a strong interest in Agricultural Mechanisation, Economic Modelling, Agronomics, Alternative energy, Comms Engineering / Remote Area Comms and Entrepreneurial Start-Ups. Matt is available to discuss these topics, and would welcome contact from anyone interested in discussing their business.

18 comments September 26th, 2007

1GB then and now..

I ‘stumbled’ across this little tid-bit – this photograph shows ‘cutting edge’ storage for 1GB from 1988 (on the left) and 1GB storage from 2005 (on the right).. 🙂

My how things do change – I noticed just the other day that USB keys now come in a 16GB flavour – that’s right.. those little floppy disks I used to take to school to trade ‘high tech’ games like tetris with my mates about 15 years ago were 1.44MB in size – I can now hold the equivalent of ~11,400 of them in a little card on my keyring – that’s incredible.


1 comment September 26th, 2007

Got a new ute :)

Brief update – I got a new vehicle today.

I’ve been driving around an ancient vehicle with 300K+ km’s for the last 5 years – and finally I decided it wasn’t really worth spending any more money on.. so today I purchased a new old ute at auction.

For those of you who aren’t from Australia, a ‘ute’ is like a pickup – it’s a uniquely Australian invention that was designed to allow farmers to have a vehicle that they could use during the week on their farm, and still be ‘beautiful’ enough to take the wife or significant other to church on Sunday without causing embarassment.

The fact they only have two seats and a v6 engine is a bit of a problem in this modern world of high fuel prices and environmental conscience though – and on that matter I feel a little guilty. There was a Prius that went for about $5K more, and I did consider it (momentarily).

If it weren’t for the fact that utes were made for dogs and dogs were made for utes and dogs aren’t allowed in ‘family cars’ and I have a dog, I’m sure I wouldn’t have got a ute – but I have horses and dogs and love the country – so i’ll stay with the ute for the moment and ride my bicycle around town to help limit global warming and waist expansion 🙂

Photo below… M

Can I run it on LPG or autogas in Brisbane?

6 comments September 13th, 2007

Danger! Multiple domain names, 1 site – why it is bad

I’ve been on an hiatus from writing here, so I thought I might break the trend by talking about the practice of creating multiple websites to ‘corner the market’ – jealously guarding your url to ensure no-one uses a variation.

An example might be registering, and then being seduced by the offer (godaddy does this regularly) to register variants of your new domain name (eg .biz, .net, .org) at a ‘special discount’ – they don’t offer fries just yet, but domain sellers really are the masters of the up-sell.

I consider registering more than one domain a bit pointless

The days of people memorising and typing a url into a browser are pretty much over – except for a few notable and brilliant exceptions with catchy names like, and other less successful or well known sites such as google and youtube most people get to a site the new-fangled way – by following links or doing a search. So, really in essence, you’re probably paying extra for not much benefit.

Furthermore, the practice can have insidious side effects – you can actually shoot yourself in the foot.

Multiple domains = Multiple sources of links

When presented with duplicate content, google often seems to pick one page as the ‘original’ and consign the others as unimportant copies, and they don’t rank well.

You could end up with a situation where google chooses a page from each of your site copies as the ‘original’ and you end up with search traffic spread between all four.

Registering Multiple domains for the same site can actually be bad for business

Links to your sites naturally tend to come with traffic – and a lot of traffic generally comes from search… so… you’ll also end up with your incoming links spread between all the copies of your site.

In such a circumstance, the meaning of synergy (the parts are greater than the whole) does NOT apply. You end up with four sites with a quarter of the links they should have rather than one strong site that aggregates all the power of the incoming links in one place – end result? You don’t rank as well as you could.

How to use your multiple domains ‘the right way’

Best practice is to use something called a 301 redirect – rather than having 4 actual copies of your site all competing with each other, a 301 redirect seamlessly redirects clients (and google) to the ‘main’ url you want to rank well. If you google “how to do a 301 redirect’ you should be on your way to understanding that a bit better.

50 comments September 2nd, 2007

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