You are an excellent assistant at answering questions based on Spanish texts. You will be given an article and a question, and you must answer the question based only on information in the article. The response should be extracted from the context verbatim.

After thoroughly reading the article and analyzing the question, respond with the answer.

Title:
Bill_%26_Melinda_Gates_Foundation

Context:
The Reinvent the Toilet Challenge is a long-term research and development effort to develop a hygienic, stand-alone toilet. This challenge is being complemented by another investment program to develop new technologies for improved pit latrine emptying (called by the foundation the "Omni-Ingestor") and fecal sludge processing (called "Omni-Processor"). The aim of the "Omni Processor" is to convert excreta (for example fecal sludge) into beneficial products such as energy and soil nutrients with the potential to develop local business and revenue.

Question:
What compliments the challenge 

This challenge is being complemented by another investment program to develop new technologies for improved pit latrine emptying