Are energy from waste plants sustainable?
The news item on energy from waste projects (News last week) was written as a good news item. However, the level of opposition to incinerators is considerable and the arguments against them are convincing.
Since they were seen in the 1990s as the answer to the landfill problem, our path to the future has become clearer to all.
Mass burning of materials that can now be recovered is obviously a mistake when we can foresee an ever increasing problem of raw material supply.
Also if these plants are producing electricity only and do not provide district heating, which is generally the case, they have an efficiency of about 25%. A further problem is that the ash still has to be disposed of so landfill issues remain.
Current proposals will result in considerable overprovision of incinerator capacity to deal with domestic waste and it is obvious that the operating companies see a lucrative market for burning commercial waste as well, making the situation even worse.
When we see more and more sustainable approaches being applied to many of our activities, it is regrettable that incineration got into the equation of how we deal with waste in the 21st century.
- Frank Oldaker (M), firstname.lastname@example.org
Are buried pipes deep enough underground?
Matt Humphrey’s letter (Letters last week) accurately highlights the importance of ambient temperatures on the incidence of water main bursts.
However, one would assume that good design practice would be to install buried water pipes below the ground frost level in the first place?
For pipe sections located above the ground frost line, the risk assessment should consider the pipe diameter as well as whether static flow conditions are likely, even for short periods of time.
Protection measures to be considered are the application of electrical trace heating and thermal insulation and cladding for all pipes up to 150mm diameter and thermal insulation and cladding for pipe diameters over 150mm to 300mm.
The correct solution will be dependent on the specific historical minimum ambient conditions for the relevant location.
I have been advising clients for over 25 years regarding the protection of water pipes for above and below ground locations, and I am frankly surprised that there is still a relatively high incidence of burst water pipes when ambient temperatures have generally been well above historical minimums!
- David Lee (M), director, Leeda Management, email@example.com
Deep level ground freezing
Matt Humphrey’s criticism last week of Ray Yalden’s letter (NCE 27 January) misses the mark. That letter does not claim that temperature does not have a clear effect on water main bursts.
On the contrary, the experienced writer states that it does. However, he makes the point that this temperature effect is not usually a result of deep-level ground freezing − as was claimed recently concerning bursts in Northern Ireland and Scotland. Nonsense?
- George Kistruck (M Ret), George@Kisruck.com
Wealth helps confer status
As most people judge status by the size of house one lives in and the type of car on the drive, perhaps the best way to enhance the status of engineers is to triple, at least, salaries.
- TW Merrick (M),Tom Merrick, firstname.lastname@example.org
Well off get better job access
This past week has seen a number of television programmes focusing on social mobility and the professions.
The conclusion drawn was that recruitment was increasingly from the higher socio-economic groups and that opportunities for working class and some middle class recruits were getting fewer and fewer.
The key determinant was not actual or potential ability but family resources and interventions and that serves the professions and the country badly.
Where the engineering profession stands was not mentioned − perhaps it wasn’t seen as a profession − but do the claims made about the professions in general apply to civil engineers?
It seems to me, and this was supported by the TV programmes, that many of my generation from the early 1960s were grammar school boys and that provided the step into a profession.
That step has more or less gone; what, if anything, has replaced it? The pool of talent from which new entrants can be recruited is now much more restricted than it had been then.
Only the figures could tell us. The ICE, like most professional bodies, does not collect data on the socio-economic background of new entrants, claiming that it would be seen as intrusive to be doing so.
Intrusive it may be, but surely if you don’t have the figures how can you recognise if there is a problem or do anything about it.
If this situation is applicable to civil engineering, what does that contribute to the lack of status of engineers, to the numbers of engineering graduates lost from the industry, and to the lack of appreciation of non-graduate careers in the industry.
- Rodney Bray (M Retd), email@example.com
Wind power and value for money
Your interview with Alistair Dutton (NCE 3 February 2011) provide useful but worrying information. It seems we are going to be paying £150bn for 25GW of North Sea wind energy capacity.
As I understand it, capacity means maximum output and the average is about 20% of this e.g, 5GW making the cost £30bn per GW average delivery.
Now consider what it might be used for. A 24MW High Speed 2 (HS2) train for example.
So the capital cost of the power facility for a single HS2 train from North Sea wind energy would be £30bn/GW x 0.024GW = £720M, or the cost of about four jumbo jets.
How can we as engineers live with introducing such massive disproportions to the world. Are we losing the plot?
- Bryn Bird (M), Bryn.firstname.lastname@example.org
Letters to the editor
NCE welcomes letters from readers. We attempt to print as many as possible, which means letters longer than 200 words are likely to be condensed.