Bagasse (/bəˈɡæs/ ^ⓘ bə-GAS) is the dry pulpy fibrous material that remains after crushing sugarcane or sorghum stalks to extract their juice. It is used as a biofuel for the production of heat, energy, and electricity, and in the manufacture of pulp and building materials. Agave bagasse is similar, but is the material remnants after extracting blue agave sap.

The word comes from bagasse (French) and bagazo (Spanish), meaning refuse or trash. It originally referred to the material left after pressing olives, palm nuts, and grapes. The word eventually came to be used in the context of processing of plants such as sugarcane and sugar beets. Today, it usually refers to by-products of the sugarcane mill.

Bagasse is the solid by-product when the liquid components are extracted from plants. Much of the core of those plants is a heterogeneous "pith" fibre. This fibre is primarily parenchyma tissue, along with bast, rind, or stem fibers of the sclerenchyma.

Here's an example chemical analysis of washed and dried bagasse:

For every 10 tonnes of sugarcane crushed, a sugar factory produces nearly three tonnes of wet bagasse. It is challenging to use this byproduct directly as a fuel because of the high moisture content, typically 40–50 percent. Instead, bagasse is typically stored prior to further processing.

For electricity production, the bagasse is stored under moist conditions. Under these conditions, the bagasse undergoes a mild exothermic process as the residual sugars slightly degrade.

For paper and pulp production, the bagasse is normally stored wet so as to facilitate the subsequent removal of any remaining sugar as well as the short pith fibres. These fibres would impede the paper making process.

Numerous research efforts have explored using bagasse in the production of bio-based materials and as a biofuel in renewable power generation.