Add CO2 factors for ferries and rewrite section.

handbook/emissions.html

@@ -28,7 +28,7 @@
   <li>Who was in their car for the outward and return journey</li>
   <li>Fuel usage (in litres) for the outward and return journey (could easily be calculated by drivers by keeping their fuel receipts)</li>
   <li>Whether their car is petrol or diesel</li>
-  <li>Channel crossing route/method</li>
+  <li>Channel crossing route/method, preferably ship name/type</li>
 </ul>
 
 <p>Per person and per journey CO2 (kg) =</p>
@@ -86,19 +86,34 @@
   <li>Input journey into: <a href="https://scif.org.uk/web/carbon-calculator/">https://scif.org.uk/web/carbon-calculator/</a>, selecting 'bus' as travel mode</li>
 </ol>
 
-<h3>Ferry calculations (not from UK)</h3>
+<h3>Ferry calculations</h3>
+
+<p>Mostly people will be doing the UK/France crossing, but some attendees will use ferries elsewhere - e.g from/to Scandinavia or Greek Islands. Good emissions data for ferries is still hard to find, but improving. Emissions vary enormously by ferry type and propulsion system. The main thing is to distinguish the basic type: Chunnel (nuclear-electric rail and thus very low-carbon), standard (displacaement) car ferries, and fast/catamaran/planing type ferries (often passenger only) which use much more fuel. Knowing the name of the ferry or propulsion type would be very helpful.<p>
+    
 <p>Data needed:</p>
 <ul>
   <li>Start and end destinations (including any via destinations which are necessary for the trip)</li>
-  <li>Whether the ferry is high speed (planing) or displacement (most car ferries). High-speed ferries have emissions similar to that of aircraft [citation needed]
+  <li>Ferry name and/or type: Chunnel (not a ferry), standard displacement or fast planing. Some channel ferries are diesel/elextric hybrids since June 2023. 
 </ul>
 
 <p>Methodology:</p>
 <ol>
-  <li>Input journey into: <a href="https://scif.org.uk/web/carbon-calculator/">https://scif.org.uk/web/carbon-calculator</a>' using 'plane' for fast ferries as travel mode and 'bus' for slow car-ferries (Temporary hack, but better than ignoring ferries completely)</li>
+  <li>Crossing distance one way (km) * ferry CO2e factor (kg per passenger-km) * Number of people in car  (gives one-way value)</li>
+  <ul>
+    <li>Chunnel: 0.011 (kg per passenger-km)</li>
+    <li>Standard car ferry: 0.1295 (kg per passenger-km)</li>
+    <li>Hybrid car ferry: 0.0777 (kg per passenger-km)</li>
+    <li>Fast ferry: ?</li>
+  </ul>
 </ol>
-Currently the calculator does not complain if you travel 'by bus' between two islands.
+<ul>
+  <li>Dover-Calais crossing distance: 44km</li>
+  <li>Dover-Dunkirk crossing distance: 66km</li>
+  <li>Others can be calculated at <a href="http://www.shiptraffic.net/2001/05/voyage-planner-marine-traffic.html">http://www.shiptraffic.net/2001/05/voyage-planner-marine-traffic.html</a></li>
+</ul>
 
+<p>References: <a href="https://thrustcarbon.com/insights/how-to-calculate-emissions-from-a-ferry-journey">https://thrustcarbon.com/insights/how-to-calculate-emissions-from-a-ferry-journey</a>, <a href="https://www.ferryhopper.com/en/blog/featured/eco-sustainable-ferry-travel">https://www.ferryhopper.com/en/blog/featured/eco-sustainable-ferry-travel</a>, <a href="https://www.getlinkgroup.com/en/our-group/eurotunnel/">https://www.getlinkgroup.com/en/our-group/eurotunnel/</a>
+</p>
 
 <h3>Gear calulations</h3>
 <p>These have not been done so far, and are hard to calculate as most manufacturers do not yet provied LCAs for their stuff, and we don't track purchase weights, but an estimate could be made from the gear/shopping lists and existing materials sources given sufficient enthusiasm.</p>