Project idea: W/S Waste Steam Ship Avfallsångbåten cleans the archipelago

Hem / Styrelse / Skrivelser / Miljöprojekt / På svenska

W/S Waste Steam Ship is driven by organic waste which produce steam in a Super Critical Water Oxidation reactor (SCWO).

The ship can be driven on all types water containing organic material such as sewage sludge, toalette waste and oil containing water. After loading a sewage sludge from a wastewater treatment plant in Stockholm or Lotsbroverket in Mariehamn, the Waste Steam Ship can sail out into the archipelago of Ålands and Stockholms to collect toalette waste from harbours and residencal houses on the islands. To drive a ship on sewage sludge is not more odd than driving buses on biogas achieved through digestion of sewage sludge. Compared to a digestion plant, a Super Critical Water Oxidation plant is more compact and gives twice as much energy from the sludge. The sludge from Lotsbroverket can with SCWO replace 275 tonne oil compared to 110 tonne oil which correspond to the biogas which is achieved by digestion. At digestion about half of the organic material remains after digestion while SCWO destructs all organic material. Produced amount of biogas (219 106 m3) has an energy value of 6 kWh/m3, which gives 1,31 GWh. However, through dewatering to 20 % DS and 30 % oorganic substances in the sludge, 275 tonne oil is replaced by 2000 tonne sludge, which gives that a too large part of the load capacity of the ship is used for the fuel. This alternative can therefore be realistic for ship that is used for collecting sludge, sewage and other organc waste, and thereby reduce the transport need by using it as a fuel for the ship, instead of transporting the collected sludge to a central treatment place. The content of organic substance in the sludge can be increased by adding grounded food waste or other biological material and also oil. A fuel tank for oil is needed both for heating the reactor to working temperature at start and to increase the organic substance to at least 3 %, which makes equipment for dewatering unnessecary. Also other organic material such as oil polluted water from ships collected in harbours can be used for driving the ship. If the content of organic substance in the water is to low, oil can be injected into the reactor. The oil injection can be controlled by the temperature. If temperature drops due to less organic substances in the water, more oil is injected into the reactor.

Water jet propulsion can be used for driving the ship. Water is pumped from inlet in the stem and ejected at the stern. Then the water passes the ship algae and other organic material in the water can be separated and added to the SCWO reactor and be used for propulsion of the ship. Also oil pollutions in the passing water can be separated and added to the reactor. The Waste Steam Ship can thereby be used for cleaning of oil discharge. Also problem witth nutrification and algal blooms can be counteracted by the ship taking up algae from the water and using the organic algae mass as fuel. Since the phosphorus content in the algae remains in the inorganic rest product, which can be used for phosphorus recovery, the shipå contributes to remove nutrients from the sea water. After a tour collecting waste the ship can deliver the produced in organic rest product to a plant for phosphorus recovery. If Stockholm Water (Köhler, 2002) accomplish the ideas to construct a SCWO plant for oxidizing sewage sludge and recovery of phosphate from the rest product, the produced rest product can be sent to Stockholm for phosphorus recovery. Since the inorganic rest product originates from all material added to the reactor, phosphorus recovery is achieved from all material collected by the shipt. Some part of the recovered phosphorus originates from the algae sseparated from the water passing through, the ship produce a nutrient uptake from the sea water which partly can compensate nutrient discharge from other sources such as agriculture and fish farming. The nitrogen in the materialet produce nitrogen gas in the reactor. To counteract global warming through carbon dioxide emission, the produced carbon dioxide can be collected in a tank and delivered for other uses.

That the oceans have turned into floating dumps has got more attention (Ny Teknik, 2012). The bulk of the waste consists of plastic, from micro particles to plastic bags is floating in water. Vessels driven on waste, which filters the water and oxidizes the waste in the engine, should help to create cleaner oceans. Much of the waste comes from the garbage dumped overboard from ships. If the garbage can be used to power the ship it becomes a waste to throw waste overboard, thus littering the oceans will be reduced.

A ship driven by a SCWO reactor can also be used as house boat. To live in ships moored at the quays of Stockholm is not alowed if the the ships not can be connected to municipal sewage, which is very difficult to achieve. However if the ship can oxidise the sewage in a SCWO reactor, there is no sewage that has to take charge of. The possibility to live in a house boat moored at a quay can give more people the possibility for attracitive living in central Stockholms. To live in a house boat gives also the possibility to rent an island with a bridge in the archepelago during the vacation. During the vacation is the house boat moored to the bridge on the archepelago island and during the rest of the year in the city near to work. Thereby more people can have the possibility to live in the archepelago during the vacations, without having to builds houses on all islands. The time then the boat is not moored at the island, others has the possibility to visit the island. For traveling between the archepelago and the city the boat is driven by the SCWO reactor. Sewage, organic waste and algae in the seawater is not enough and addition of other fuel is nessecary. Many boats going in the archepelago separating algae from the sea water will contribute to reduce nutrification and thereby counteract algals blooms.

The project can be divided i diifferent phases:

  1. A prestudy for estimation of it is possible to build a SCWO reactor small and compact enough to be used on a ship.
  2. Make authoroties interested in the procet and find sponsors in order to the collect money needed for building or purchasing a ship.
  3. Building the ship or converting a ship by changing the machinery with a SCWO reactor.
  4. Study of methods for separating of organic material from sea water taken up by the ship.

Köhler, N. (2002) Tvist om bästa slamrening, Ny Teknik, 8 maj.
Levlin E. (2003) Bedömning av utsläpp av växthusgaser och andra luftföroreningar på Åland. Åländsk utredningsserie 2003:2, ISSN 0357-735X,
von Schultz C. (2012) Östersjön är en flytande soptipp Ny Teknik, week 25,

Erik Levlin