A suitable approach might be the SITC classification as used in the OECD Statistics on International  Trade by Commodity.

 See http://www.oecd-ilibrary.org/trade/international-trade-by-commodity-statistics/volume-2014/issue-5_itcs-v2014-5-en

Thanks

The US International Trade Commission uses these classification system. You can check their web.

Commodity Description Lookup

Harmonized Tariff Schedule (HTS)

2 Digit HTS Descriptions

4 Digit HTS Descriptions

Standard Industrial Classification (SIC)

1 Digit SIC Descriptions

2 Digit SIC Descriptions

3 Digit SIC Descriptions

4 Digit SIC Descriptions

Standard International Trade Classification (SITC)

1 Digit SITC Descriptions

2 Digit SITC Descriptions

3 Digit SITC Descriptions

4 Digit SITC Descriptions

5 Digit SITC Descriptions

North American Industry Classification System (NAICS)

2 Digit NAICS Descriptions

3 Digit NAICS Descriptions

4 Digit NAICS Descriptions

5 Digit NAICS Descriptions

6 Digit NAICS Descriptions

Import End Use Codes

1 Digit END USE Descriptions

2 Digit END USE Descriptions

3 Digit END USE Descriptions

5 Digit END USE Descriptions

Export End Use Codes

1 Digit END USE Descriptions

2 Digit END USE Descriptions

3 Digit END USE Descriptions

5 Digit END USE Descriptions

Hello!

The most common classifications are:

1. SITC - the Standard International Trade Classification:

http://ec.europa.eu/eurostat/statistics-explained/index.php/Glossary:Standard_international_trade_classification_%28SITC%29

2. HS - Harmonized System:

http://ec.europa.eu/taxation_customs/customs/customs_duties/tariff_aspects/harmonised_system/index_en.htm

3. CN - Combined Nomenclature:

http://ec.europa.eu/taxation_customs/customs/customs_duties/tariff_aspects/combined_nomenclature/index_en.htm

4. BEC - Classification by Broad Economic Categories:

http://unstats.un.org/unsd/iiss/Classification-by-Broad-Economic-Categories-BEC.ashx

Best regards,

Monica

Thanks. Hopefully these links will help further aggregate commodities into three main categories: agriculture, minerals, manufactures.