Energy trading companies have branched out into buying refining capacity, storage and oil and gas fields to complement their core activities.
A record rally last year drove prices to nearly $150 a barrel and increased the cost of trading for some firms that were punished by hefty margin calls.
Then the financial rout that began last year had a drastic impact on the availability of credit.
Some trading houses have sold off assets. For others, there are bargains to be had and they could make acquisitions provided they can get the credit and assets fit with specific trading needs.
Below are some details about the main independent trading houses in alphabetical order. Information is taken from company websites and Reuters.
Glencore International AG GLEN.UL
Founded in 1974, Swiss-based Glencore International supplies a wide range of commodities -- including metals, minerals, crude oil, oil products, coal and agricultural products.
Turnover for fiscal 2008 was $152.2 billion.
Initially, Glencore focused on the physical marketing of ferrous and non-ferrous metals, minerals and crude oil. It then expanded into oil products and coal and in 1982 acquired an established grain marketing company.
Glencore has three main business groups -- metals and minerals, energy products and agricultural products.
Together with subsidiaries, it has investment in a wide range of commodity production and says it is one of the largest non-integrated oil suppliers by volume.
Glencore's net profits fell 8.4 percent in 2008 to $4.75 billion and it has sold off some assets.
In March, Colombian state oil firm Ecopetrol said Glencore had agreed to sell to it its assets in the Cartagena refinery, Colombia, for $549 million.
Also in March, mining group Xstrata Plc (XTA.L) approved the purchase of the Prodeco coal mine in Colombia from Glencore, Xstrata's biggest shareholder, with a nearly 35 percent stake.
In line with other mine operators, Glencore has also shut in production in some of its mines in response to steep falls in commodity demand.Gunvor International B.V...MUCH MORE